Honeywell disputed the allegations.

"We believe there is no factual or legal basis for the Justice Department's case against Honeywell and we intend to vigorously defend against these claims," Honeywell said in an e-mailed statement. "We did not manufacture the fiber which was the cause for the DoJ's initial investigation in this matter and did not manufacture the vests that were sold to the government. We are aware of no instances where any vest containing Z-Shield technology failed during use in the field, and in fact, vests containing Z-Shield have saved many lives."

The lawsuit is the result of an ongoing investigation by a range of government agencies, including divisions from the Air Force and Army, the Justice Department's Civil Division, the FBI, the General Services Administration's Office of the Inspector General, and the Defense Criminal Investigative Service. The Army and Air Force divisions "were part of an investigation to check out these things" and determine whether the defects had any application to their services, the Justice Department's Charles Miller said.

"The United States will not tolerate a company withholding key scientific information that places our first-responders at risk unnecessarily," said Gregory Katsas, the acting assistant attorney general for the Civil Division, according to a Justice Department announcement. "The Justice Department will take the steps needed to ensure that a company providing a potentially life-saving product discloses any known defects so that the United States can make an informed decision on whether or not to buy the product."

Honeywell International is facing a lawsuit by the United States claiming that the company knew Zylon Shield, which Honeywell made and sold as the as the key ballistic material in bullet-proof vests, degraded in hot and humid conditions but didn't tell the maker of the vests, Armor Holdings, or the United States.

However, a Justice Department spokesman said the bulletproof vests weren't used for the military, but for law enforcement only, mostly police and sheriffs' departments.

The Justice Department said it is suing Honeywell under the False Claims Act, alleging Honeywell had scientific data showing that Zylon Shield quickly degraded over time, especially in hot and humid conditions, and that Honeywell knew that made vests made with Zylon unfit to use.