BOSTON, Mass. — The FBI has solved part of the mystery, but the government is seeking help to solve the largest art theft in U.S. history. Anyone who can help may be eligible for a $5 million reward.

After 23 years of intense investigation, federal officials announced on March 18 that they know who committed the theft, but they need the public’s help to locate the 11 paintings and two art objects stolen from Boston’s Isabella Stewart Gardner Museum on March 18, 1990. Included in the heist were rare paintings by Rembrandt and Johannes Vermeer. The 13 items are worth $500 million.

Richard DesLauriers, head of the FBI’s Boston office, said at a press conference that agents “have made significant investigative progress in the search for the stolen art from the museum. We’ve determined in the years after the theft that the art was transported to the Connecticut and Philadelphia regions, but we haven’t identified where the art is right now, and that’s why we are asking the public for help.”

Agents have discovered intriguing evidence to suggest that the robbery was an inside job, and a former night watchman could have been in on the job all along, or perhaps knows more about the heist that he has admitted. He has not been charged, nor are they calling him a suspect.

Federal prosecutors questioned ex-watchman Richard Abath last fall on many aspects of the case and discoveries uncovered in recent years. Abath has recently begun to talk about the case, and admits some of his actions during the night of the robbery are hard to explain. He strongly insists; however, he had nothing to do with the theft.

On March 18, 1990, Abath, who was working as a part-time security guard at the time, told agents he opened the doors to the museum to two men who were dressed as Boston police officers. He said the police officers told him they were there to investigate a disturbance. Abath is writing a manuscript about the robbery, and he shared it with a Boston Globe reporter. Abath wrote, “There they stood, two of Boston’s finest waving at me through the glass. Hats, coats, badges, they looked like cops. I buzzed them into the museum.”

Abath was 23 years old on the day of the robbery. Abath, now 46, told the Boston Globe he passed two lie detector tests immediately after the crime. Investigators have questioned him about certain aspects of his statements that draw his involvement into question.

“I totally get it,” he said. “I understand how suspicious it all is, but I don’t understand why (investigators) think that I should know an alternate theory as to what happened, or why it did not happen.”

Abath, now a teacher’s aide, lives in Brattleboro, Vt. with his wife in a modest apartment with his two children from an earlier relationship.

The investigation is headed by U.S. Attorney Carmen M. Ortiz in Boston, who said the case is active and, “at times, fast moving.” Even though the statute of limitations for prosecuting the robbery ended in 1995, Ortiz said she can still charge anyone with possessing stolen artwork. However, Ortiz added, she would grant immunity to anyone for helping recover the art treasures.

The robbery’s storyline

On the night of the robbery, Abath allowed two men posing as Boston police officers into the museum at 1:24 a.m. on March 18, 1990. When they entered, one of the phony police officers questioned Abath, and told him, “I think there is a warrant out for your arrest,” according to Abath’s account.

They asked for his identification and then handcuffed him. Abath and another security guard, who was also handcuffed after returning from making his security checks, were wrapped in duct tape and taken to different areas of the basement. They were discovered eight hours later by legitimate police officers.

FBI agents claim the thieves remained in the museum for 81 minutes, which has baffled them. They are also puzzled why the thieves didn’t take a prized painting, Titan’s Rape of Europe, considered a masterpiece worth millions of dollars.

The stolen art include Rembrandt’s The Storm on the Sea of Galilee, 1637; Johannes Vermeer’s The Concert, 1658-1660; Rembrandt, A Lady and Gentleman in Black, 1633; Edouard Manet’s Chez Tortoni, 1878-1880; Govaert Flinck, Landscape with an Obelisk, 1838; Degas’ La Sortie de Pesage; Degas’ Program for an Artistic Soiree; Degas’ Program for an Artistic Soiree, Study 2, 1884; Degas’ Cortege aux Environs de Florencel; Rembrandt’s Self-Portrait, 1634; Degas, Three Mounted Jockeys; and two art objects, a French finial in the form of an eagle, 1813-1814; and a Chinese Bronze Beaker or Ku, 1200-1100 B.C.

Special agent Geoff Kelly, who heads the FBI investigation, said, “with these considerable developments over the last couple of years, it’s likely over time someone has seen the art hanging on a wall, placed above a mantel or stored in an attic.” Kelly pleaded, “We want that person to call the FBI.”

Those who have seen any of these items or have information should call the Garner Museum in Boston or the FBI’s hotline at 1-800-CALL-FBI.