WASHINGTON (CNN) -- DNA evidence from the deadly 2001 anthrax mailings led authorities to a suspect who officials say killed himself, according to a source familiar with the investigation.
Biodefense researcher Bruce E. Ivins died Tuesday from an apparent suicide, officials say.
The DNA linked the anthrax used in the mailing to a flask used in Bruce Ivins' lab at the U.S. Army Medical Institute of Infectious Diseases, said the source, who was not authorized to speak publicly about the case.
Officials say Ivins, a scientist at the lab in Fort Detrick, Maryland, committed suicide. He was found unconscious at his home July 27 and died at a Maryland hospital Tuesday, the same day he was to have discussed a plea deal with prosecutors.
Authorities may release their evidence against Ivins, 62, as soon as this week before closing the case, sources said.
No charges have been made public, and no arrests have been made in the anthrax probe.
Five people died and more than a dozen others became ill after letters containing anthrax were sent to congressional offices and media organizations soon after September 11, 2001, terrorist attacks.
Among those who died were two postal workers. Two contaminated letters were sent to senators, exposing 30 staffers.
Ivins, of Frederick, Maryland, worked for decades in the biodefense lab at Fort Detrick, where he was trying to develop a better vaccine against the anthrax toxin.
The FBI traced the anthrax used in the attacks to the lab by using a new genetic technology, a U.S. official familiar with the probe said.
Authorities were looking at whether Ivins released anthrax as a way to test a vaccine he was working on, another official said.
At the time of his death, Ivins was under a temporary restraining order sought by a social worker who counseled him in private and group sessions. She accused him of having harassed, stalked and threatened violence in the previous 30 days.
The woman told the court in her complaint that Ivins had spent time at a mental health facility.
CNN's Kevin Bohn and Brianna Keilar contributed to this report.