In an interview with WFXT-TV, the Fox-owned station in Boston, Geoff Kelly said the investigation remains active 24 years after the theft.
In 1990, two men disguised as police officers talked their way into the museum and overpowered the security guards. They escaped with possibly the biggest haul ever of stolen art, including Rembrandt's Christ on the Sea of Galilee and The Concert, one of only 34 definitive works by the Dutch master Johannes Vermeer, a Rembrandt etching, a Manet, and five Degas drawings. The thieves also took a Shang dynasty bronze beaker from China and an eagle-shaped finial or end-piece from a Napoleonic flag.
Kelly, in his first TV interview since taking charge of the case 11 years ago, said that over the years sources agents believe are credible have reported seeing the missing art. He said it was last seen in Philadelphia.
"When this case originally went down, the suspect list was pages long," Kelly said, adding that it has been "whittled down" considerably over the years.
While well-known artworks sell for millions of dollars when they come on the market, experts believe many thefts are carried out to get potential bargaining chips because stolen works cannot be sold openly. In the Isabella Stewart Gardner theft, the FBI has offered a $5 million reward for recovery of the paintings and federal prosecutors have offered immunity.
Kelly said there are three persons of interest in the investigation, Carmello Merlino and Robert Guarente, both of whom are dead, and Robert Gentile. Gentile's home in Manchester, Conn., was searched in 2012 and no art was found, although investigators found clothing with police and FBI insignia and other paraphernalia like two-way radios.
In the 1990s, the FBI learned from informants that Merlino wanted to return the Rembrandt painting for a reward. But the deal fell through when Merlino was arrested in connection with an armored car robbery.
Under the terms of Isabella Stewart Gardner's will, the contents of her Italian-style palace on the Fenway must remain in the arrangement she decreed. That means the places where the stolen paintings hung remain empty.