Federal
 prosecutors have begun presenting evidence to a grand jury considering a
 case against the leader of the New York State Senate, Dean G. Skelos of
 Long Island, and his son, according to people with knowledge of the 
matter.

Investigators
 have served a number of subpoenas in recent weeks, including several to
 state senators on Long Island, and federal prosecutors have interviewed
 people who have had dealings with Adam Skelos, the Republican senator’s
 son.
 
News of the investigation follows the arrest this year of Assemblyman Sheldon Silver,
 a Manhattan Democrat, and his resignation as speaker; any criminal case
 against Senator Skelos, the majority leader, would throw the Capitol 
into further tumult.
Prosecutors
 and the F.B.I. have focused on at least two areas in their 
investigation, zeroing in on Adam Skelos’s business dealings, according 
to several people with knowledge of the matter.
One
 focal point has been Adam Skelos’s hiring by an Arizona company, AbTech
 Industries, as well as a storm-water treatment contract that AbTech was
 awarded by Nassau County — the senator’s political backyard — even 
though the company was not the low bidder. Another area of inquiry has 
been a $20,000 payment to Adam Skelos from a title insurance company 
that he never worked for.
    
                Mr. Skelos being sworn in this year, with his wife, Gail, and his son, Adam, who is also part of the investigation.
                        
            Credit
            Mike Groll/Associated Press        
            
     
According
 to people familiar with the questions being asked by federal 
authorities, investigators are seeking to determine whether Senator 
Skelos exerted any influence in matters involving AbTech. They are also 
examining whether his son’s hiring as a consultant was part of a scheme 
in which the senator, in exchange, would take official action that would
 benefit AbTech or another company, Glenwood Management, a politically 
influential real estate developer that has had ties to AbTech.
Any
 such action could pose a conflict of interest or potentially violate 
federal corruption statutes. It is unclear what actions, if any, Senator
 Skelos has taken in connection to his son’s business dealings, or how 
they relate to state government; neither man has been accused of 
wrongdoing.
All
 of the people who spoke about the investigation did so on the condition
 of anonymity because of the delicate nature of the subject.
The investigation is being conducted by the office of Preet Bharara,
 the United States attorney for the Southern District of New York, who 
has embarked on an assault against graft and other political misdeeds in
 Albany, describing the capital as a “caldron of corruption.” His 
critics have accused him of grandstanding, and say his unusually blunt 
public condemnations of how business is done in Albany have crossed the line for a federal prosecutor.
Glenwood Management, one of the state’s largest campaign donors, also surfaced in the criminal case
 against Mr. Silver, who is accused of steering Glenwood and another 
developer to a law firm that gave him a cut of their fees. Glenwood has 
not been accused of wrongdoing in the Silver case or in the 
investigation involving the Skeloses.
Adam
 Skelos, 32, when asked about the investigation during a brief interview
 outside his house, said he was surprised to learn he was the focus of a
 federal inquiry. “I had no idea that this was even an issue,” he said. 
“I got to tell you, this is really unexpected.”
Senator Skelos, 67, and his son did not respond to written questions from The New York Times.
The
 inquiry into the senator and his son comes at a chaotic time in Albany.
 In January, state government was rocked when Mr. Silver was arrested on
 corruption charges brought by Mr. Bharara’s office.
The case against Mr. Silver and the investigation of Mr. Skelos grew in some measure out of the Moreland Commission,
 an anticorruption panel that Gov. Andrew M. Cuomo created in 2013. The 
governor, a Democrat, abruptly disbanded the panel last year as part of a
 budget deal he negotiated in large part with Mr. Skelos and Mr. Silver;
 Mr. Bharara’s office then opened a criminal inquiry into the shutdown.
As
 with Mr. Silver’s, Mr. Skelos’s outside income as a lawyer has come 
under federal scrutiny. In the senator’s case, his law firm, Ruskin 
Moscou Faltischek, received a federal grand jury subpoena in 2014. In January, 
WNBC-TV
 reported that federal investigators were looking into Mr. Skelos’s 
outside income, with a focus on his ties to the real estate industry. 
The law firm has not been accused of any wrongdoing.
Mr. Bharara’s office and the Federal Bureau of Investigation declined to comment.
Adam
 Skelos, who lives blocks from his father in a well-kept neighborhood in
 Rockville Centre in Nassau County, is involved in an array of 
businesses stretching from Long Island to Albany, according to a review 
by The Times. In recent years, he has held positions at title insurance 
companies.
But
 it is his connection to AbTech Industries, which sells spongelike 
filters to remove pollutants from storm water, that brings him in 
particular proximity to state and local government.
For
 a small business in Arizona, AbTech would seem unlikely to be 
associated with Glenwood, which develops rental apartments in New York 
City.
Glenwood’s
 link to AbTech is buried in the regulatory filings of AbTech’s publicly
 traded parent company. In 2011, one of its largest investors was a 
company that shared an address on Long Island with Glenwood’s corporate 
headquarters.
Two
 men with close ties to the real estate company — Charles Dorego, a top 
Glenwood executive, and Steven Swarzman, a grandson of Glenwood’s 
longtime principal, Leonard Litwin — have signed public records filed by
 the company that invested in AbTech’s parent company, Abtech Holdings. 
Mr. Swarzman became friends with AbTech’s founder in Arizona, and, 
impressed by the environmental sponge, became AbTech’s East Coast 
distributor, according to a 2006 article in Newsday.
AbTech’s sponge has met with limited commercial success. In fact, the parent company is not profitable and trades
 at roughly 30 cents a share. But AbTech got what appeared to be a big 
break in 2013, when it secured a contract worth up to $12 million from 
Nassau County for the design, installation and operation of a 
storm-water treatment system.
Adam
 Skelos introduced officials at the Nassau Department of Public Works to
 AbTech, said Mary Studdert, a spokeswoman for the agency. Ms. Studdert 
said Mr. Skelos had roughly a dozen meetings and phone calls with a 
senior public works official; that person was a member of the committee 
that evaluated the proposals for the storm-water project.
The
 contract was awarded to AbTech, even though another company submitted a
 substantially lower bid. County officials at the time contended that 
AbTech would ultimately provide the best value, county documents show.
But
 the low bidder, Newport Engineering, seemed mystified by the process. 
Nicholas J. DeSantis, the company’s president, said that the Public 
Works Department never acknowledged receiving his bid and that he was 
not notified that the contract had been awarded.
So
 far, AbTech has been paid only a small amount of the potential value of
 the contract, according to the county comptroller’s office. In an 
unusual arrangement for a local public works project in New York, the 
contract calls for AbTech to oversee both design and construction, 
requiring Nassau to secure state legislative approval for the contract 
to go forward as intended. No lawmaker has sponsored the necessary 
legislation, Ms. Studdert said.
The
 Nassau County executive, Edward P. Mangano, a Republican who held a 
news conference in 2014 to publicize the AbTech contract, did not 
respond to questions sent to his spokesman.
AbTech
 has not been accused of wrongdoing and did not respond to written 
questions from The Times. A lawyer for Glenwood, Alan Levine, declined 
to comment.
In
 addition to AbTech’s effort to solicit government contracts, a 
subsidiary of its parent company has lobbied in Albany on several 
matters, including engineering issues, although it is unclear whether 
those activities are under federal scrutiny.
Federal
 investigators have also focused on a one-time $20,000 signing bonus 
paid to Adam Skelos by American Land Services, a title insurance firm, 
according to people with knowledge of the matter. Mr. Skelos never went 
to work at the company and did not return the money, the people said.
American
 Land Services also has at least one indirect link to Glenwood, although
 it is not known whether that is under scrutiny by federal authorities. 
Property records show that in June 2014, a senior executive at American 
Land Services paid $330,000 for an undeveloped South Carolina vacation 
property along a golf course on Kiawah Island. The executive, Tom Dwyer,
 the company’s chief operating officer, bought the parcel from Mr. 
Dorego, the Glenwood executive, who personally financed Mr. Dwyer’s 
mortgage.
Neither
 Mr. Dwyer nor other executives at American Land Services responded to 
requests for comment by phone and email. Mr. Dorego declined to answer 
questions, telling a reporter, “I have nothing to say.”