Federal authorities have executed search warrants on a Long Island businessman who is a longtime friend of Rep. Randy "Duke" Cunningham (R-Calif.) -- an apparent sign that prosecutors are widening their criminal investigation of the veteran House member.

Agents from the FBI, the Internal Revenue Service and the Defense Criminal Investigative Service executed the search warrants Thursday, Special Agent Jan Caldwell of the FBI office in San Diego said in a statement yesterday. The statement did not say whose property was searched, but sources said it belonged to Thomas T. Kontogiannis of Glen Head, N.Y.

Kontogiannis said in interviews in July that he has known Cunningham for years and bought the congressman's 65-foot yacht, the Kelly C, for $600,000 in 2002 before spending an additional $100,000 fixing it up. He also helped the congressman obtain a second mortgage on a new home in Rancho Santa Fe, Calif., in 2003, he said. Kontogiannis did not return phone calls yesterday.

A federal grand jury in San Diego has been investigating Cunningham since newspapers there reported in June that a Washington defense contractor, Mitchell J. Wade, had apparently done financial favors for the congressman. Wade allegedly bought Cunningham's house at an inflated price and allowed the congressman to live rent-free on Wade's 42-foot yacht, the Duke-Stir. In civil court papers, prosecutors have characterized the home sale as a violation of the federal bribery statute. No criminal charges have been filed.

Cunningham has denied wrongdoing. He has announced that he will not seek reelection to Congress next year.

On July 1, authorities searched Wade's Washington-based business, home and boat as well as Cunningham's home in Rancho Santa Fe.

In August, federal agents searched the home and office of Brent Wilkes of San Diego, another defense contractor, who had millions of dollars in government contracts. A Pentagon official recalled Wilkes and Cunningham calling him to seek release of funds appropriated for a program Wilkes's company was seeking.

Cunningham's lawyers said in July that the congressman's "business dealings with Mr. Kontogiannis have been entirely proper."

The Washington Post reported later that month that Cunningham had written to a prosecutor in Queens, N.Y., inquiring about Kontogiannis in 2000, when the businessman was under investigation for allegedly bribing a school superintendent. Kontogiannis was indicted but later pleaded guilty to a misdemeanor charge of attempting to commit fraud and agreed to pay nearly $5 million to settle the case.