Yesterday marked the seventh anniversary of the infamous Isabella Stewart Gardner Museum holdup, in which two thieves dressed as police officers walked into the world-famous house museum in the Fenway, tied up security guards, and walked out a few hours later with one of the largest hauls of stolen art in modern history.

Having failed to find the Gardner's priceless missing art and artifacts -- a cache that includes two Rembrandts and a rare Vermeer -- the FBI went on line yesterday in a new effort to solve the theft. The museum board of trustees has also stepped up its efforts to recover the art treasures, upping the reward it's offering for the safe return of all items in good condition from $1 million to $5 million.

The FBI says that hundreds of interviews and leads -- including a recent sighting of Vermeer's "The Concert" through a Charlestown window -- have yet to lead to the art thieves. (The Charlestown "Vermeer" turned out to be a realistic reproduction.)

The Gardner Museum art theft will now be featured on the FBI's home page on the Internet, said Barry W. Mawn, special agent in charge of the Boston FBI Office, yesterday. The home page has received an average of 200,000 hits a day since it went on line in 1996, said Mawn. The agency has even had a fugitive on its "10 Most Wanted" list surrender after he learned his name was on the 'Net, Mawn added.

The Gardner-theft web site will feature full-color depictions of the stolen items along with a brief description of each. It will also include a hotline number (742-5533) that tipsters with information can call.

The Gardner Museum plans to link its own web site to the FBI's so that visitors to the Gardner site can learn more about the stolen items.

The FBI's Gardner-theft Internet home page is at www.fbi.gov (select "Major Investigations"). The Gardner's web site is located at www.boston.com/gardner.

Copyright Boston Globe Newspaper