WASHINGTON (Reuters) - Federal authorities investigating anthrax attacks that have killed five people are examining the activities of a senior research scientist who was twice fired from a company that produces the deadly bacterium, ABC News reported on Wednesday.

Citing federal authorities, the network said the scientist, once employed at the Battelle Company, a secret anthrax-producing facility in Columbus, Ohio, made a threat to use anthrax in the days after the Sept. 11 attacks on the United States.

According to ABC, the United States has been producing small quantities of weapons-grade anthrax for several years at two secret locations -- the U.S. Army Dugway Proving Ground in Utah and at the Battelle Company, which does the work for the Central Intelligence Agency and the military.

Potent anthrax-tainted letters were sent to two U.S. senators and to media outlets by an unknown perpetrator in the aftermath of the Sept. 11 attacks on New York and Washington. Five people have died from inhalation anthrax since early October and 13 have been infected.

As part of its investigation into the anthrax cases, the FBI is interviewing current and former scientists at Battelle and the Utah facility. Some 200 U.S. scientists dealt with the anthrax program over the last five years, ABC said, citing federal authorities.

FBI and Defense Department officials had no comment on the ABC report, saying the anthrax probe was an ongoing investigation.

Battelle said it could not comment on the report. "We're cooperating fully with the investigation but we can't comment specifically on former personnel or an ongoing investigation," Battelle spokeswoman Katy Delaney said.

Battelle describes itself as a company that serves "industry and government in developing new technologies and products."

"We insert technology into systems and processes for manufacturers, pharmaceutical and agrochemical industries; trade associations; and government agencies supporting energy, the environment, health, national security, and transportation," the company said on its Web site.

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