Rembrandt's "The Storm on the Sea of Galilee," one of the works stolen from the Gardner Museum.

Federal officials involved in investigating the 1990 Gardner Museum heist--considered to be the largest museum theft in history--have plans to intensify their search for the missing work, which is valued at $500 million. Two houses, with loose ties to the late mob boss Robert Guarente, have been searched in the last eight months, according to the Boston Globe.

The Globe reports:

Officials are still finalizing plans for the public awareness campaign, but say it could go international and could, like the [James “Whitey’’] Bulger campaign, use billboards and television advertisements.

The campaign would reintroduce the public to the 13 stolen masterworks - including works by Rembrandt, Vermeer, Degas, and Manet - and try to solicit information concerning their whereabouts, officials said.

Investigators are also offering the possibility of immunity from criminal prosecution to anyone with information about the crime. The museum has offered a $5 million reward for the return of the paintings in good condition.

There are a lot more details to this story, so have a look here.