Washington ? His decades-long obsession with a college sorority may link a former Army biowarfare scientist to four anthrax-laced letters dropped off at a New Jersey mailbox in 2001, authorities said Monday in the latest twist of one of the most bizarre unsolved crimes in FBI history.

U.S. officials said Bruce Ivins’ fixation with Kappa Kappa Gamma could explain one of the biggest mysteries in the case: why the anthrax was mailed from Princeton, N.J., 195 miles from the lab it’s believed to have been smuggled from.

Still, authorities acknowledge they cannot place Ivins in Princeton the day the anthrax was mailed. And the curious explanation connecting the scientist and a sorority is unlikely to satisfy his friends and former co-workers who question what motive the married father of two might have had for unleashing the attack.

Ivins, 62, killed himself last week as the Justice Department prepared to indict him on capital murder charges for the deaths of five people who were poisoned by the anthrax in the weeks following 9/11. His attorney maintains he would have been proven innocent were he still alive.

The mailbox just off the campus of Princeton University where the letters were mailed sits about 100 yards away from where the college’s Kappa Kappa Gamma chapter stores its rush materials, initiation robes and other property. Sorority members do not live there, and the Kappa chapter at Princeton does not provide a house for the women.

Multiple U.S. officials told The Associated Press that Ivins was obsessed with Kappa Kappa Gamma, going back as far as his own college days at the University of Cincinnati when he apparently was rebuffed by a woman in the sorority. The officials all spoke on condition of anonymity because they were not authorized to discuss the case publicly.

There is nothing to indicate Ivins was focused on any one sorority member or other Princeton student, the officials said. Instead, officials said, Ivins’ e-mails and other documents detail his long-standing fixation on the organization.

An adviser to the Kappa Kappa Gamma chapter at Princeton, Katherine Breckinridge Graham, said Monday she was interviewed by FBI agents “over the last couple of years” about the case. She said she could not provide any details about the interview because she signed an FBI nondisclosure form.

However, Graham said there was nothing to indicate that any of the sorority members had anything to do with Ivins.

Kappa Kappa Gamma executive director Lauren Paitson, reached at the sorority’s headquarters in Columbus, Ohio, initially told an AP reporter Monday afternoon she would provide a comment shortly. She did not answer subsequent phone messages or e-mails seeking that response.

Had he lived, authorities had planned to argue that Ivins could have made the seven-hour round trip to Princeton from the Fort Detrick lab in Frederick, Md., after work. One official said investigators were working off the theory that Ivins chose to mail the letters from outside the sorority’s Princeton chapter to confuse the government if he ever were to emerge as a suspect in the case.