After years of questioning the conclusion and methods of an FBI investigation into the 2001 anthrax attacks that killed five people and sickened dozens of others, Rep. Rush Holt (D-Hopewell) announced yesterday that the U.S. Government Accountability Office (GAO) is opening an inquiry into the matter.

Holt, along with a handful of other legislators, had sent a letter to the GAO in May requesting an investigation into the FBI’s handling of the case. The FBI officially closed the case in February after concluding in 2008 that Dr. Bruce Ivins, a former biodefense scientist, was the sole culprit in the attacks.

Ivins, a resident of Frederick, Md., committed suicide shortly before government investigators planned to formally file charges against him.

“In the wake of the bungled FBI investigation, all of us — but especially the families of the victims of the anthrax attacks — deserve credible answers about how the attacks happened and whether the case is really closed,” Holt said in a statement yesterday.

Holt has charged in the past that the FBI investigation failed to address basic questions including Ivins’ motive and his connections with the local area.

Investigators determined that at least one of the letters was sent from a mailbox on Nassau Street in Princeton Borough. The letters were sorted at a postal service facility on Route 130 in Hamilton, where several employees became ill.

"The American people need credible answers to many questions raised by the original attack and the subsequent FBI handling of the case," Holt said. "I'm pleased the GAO has responded to our request and will look into the scientific methods used by the FBI."

The GAO's investigation will look to address a handful of specific questions as requested by Holt.

He asked the agency to identify and judge the quality of the microbial and technical forensics methods employed by the FBI in concluding Ivins was responsible for the attack. He asked what, if any, scientific concerns and uncertainties remain after the closure of the official investigation. Finally, he wanted to determine what agencies are responsible for monitoring high containment laboratories.

However, officials with the GAO, in accepting Holt’s request for an inquiry, admitted that its efforts may be hampered by lack of access to classified material.

“Please know that we may encounter challenges to our access to sensitive and classified information from the FBI and the intelligence agencies,” Ralph Dawn Jr., managing director of congressional relations for the GAO, said in a letter to Holt last month.

In 2008, the FBI commissioned its own inquiry from the National Academy of Sciences (NAS) into the results of its investigation. The results of the NAS report are expected to be released later this year.

Holt has also introduced legislation calling for a formal congressional commission to investigate the attacks. Similar to the 9/11 Commission, the panel would hold hearings and be granted subpoena power.

Officials with the Obama administration earlier this year said the president would veto any such legislation, saying it would be redundant in the wake of the FBI and NAS investigations.

Contact Matt Fair at mfair@njtimes.com or at (609) 989-5707.