FBI Searches Home of Reputed Mobster Suspected in Boston Art Heist The FBI is hoping to solve one of the country’s most enduring mysteries.

 -- The search for missing art stolen more than two decades ago from Boston's Isabella Stewart Gardner Museum has taken FBI agents to six continents around the world. But the most active lead seems to be in the backyard of an aging mobster in a small town in Connecticut.

Boston FBI field office spokeswoman Kristen Setera confirmed to ABC News that the “FBI is conducting court-authorized activity at 69 Frances Drive in Manchester, [Connecticut], in connection with an ongoing federal investigation,” but declined to comment further.

It is the third time the FBI has executed search warrants in and around that particular ranch house, the home of Robert “Bobby the Cook” Gentile, who is currently serving a 2-and-a-half-year federal sentence on unrelated drug and gun charges that came with his 2015 arrest by the FBI.

Gentile, who pleaded guilty to gun and drug charges, has repeatedly denied any connection to the stolen art and once famously muttered in court that his involvement in the heist was “lies, lies, all lies.” His lawyer, Rome McGuigan, told ABC News that his client knows nothing.

"He laughed and he couldn’t believe they were, that they were at his house again, and he said, this is a quote, ‘They ain’t gonna find nuttin,’" McGuigan said.

Among the stolen pieces were three Rembrandts, including his only seascape, "Storm on the Sea of Galilee," along with one of only 31 known works by Vermeer, "The Concert."

In a court filing obtained by ABC News, McGuigan alleged that the government was using the drug and gun charges as a way to force his client to produce the Gardner Museum paintings. He also said that the government had used informants to prod him into “talking about the paintings.”

Assistant U.S. Attorney John Durham acknowledged in a separate court filing that the FBI "tasked" a mob informant "to go see Gentile and engage him in general conversation” in 2010. The informant was instructed to "pay particular attention to anything Gentile might say about the Gardner Museum theft, but not to initiate any conversation on that topic."

According to Durham, Gentile failed a lie detector test administered by the FBI when asked questions including: “Did you know those paintings would be stolen before it happened?”; “Did you ever have any of those stolen paintings in your possession?”; and “Do know the current location of any of those paintings?”

Gentile answered no to each question but “the results of the polygraph,” the government claimed in the filing, established he “was not being truthful” about the 13 paintings stolen from the Gardner Museum in March 1990. The infamous heist remains unsolved.

Anthony Amore, the security director for the Isabella Stewart Gardner Museum, referred all questions about yesterday’s activities to the FBI. It remains unclear what was recovered, if anything, in yesterday's search.