The Justice Department is investigating whether a company sold defective bulletproof vests for President Bush, federal agents and local police, and then waited nearly two years to alert customers that the body armor could be unsafe.

A former research chief for Second Chance Body Armor Inc. is cooperating with the criminal investigation and testified this month that the Secret Service tested and bought some of the defective vests for the president and first lady Laura Bush. The Pentagon obtained the same armor for elite troops who guard generals, according to transcripts.

Many sales occurred well after Michigan-based Second Chance had been alerted that the Japanese-made Zylon synthetic material in the vests was degrading faster than expected from heat, light and moisture exposure, allowing bullets to potentially penetrate the armor, according to the former employee's testimony and other company documents.

Prosecutors have gathered documents showing that Second Chance was alerted as early as 1998 by the Japanese material maker, Toyobo Co., that there were problems with Zylon maintaining its protective properties under certain conditions.

By 2001, Second Chance's research chief, Aaron Westrick, was pleading unsuccessfully with his company's president to replace the vests after his own tests showed them degrading rapidly, the memos show.

"Lives and our credibility are at stake," Westrick wrote then-Second Chance president Richard Davis in a Dec. 18, 2001, memo. "We will only prevail if we do the right things and not hesitate. This issue should not be hidden for obvious safety issues and because of future litigation."

Westrick urged Davis to "immediately notify our customers of the degradation problems," let those with pending orders cancel them and cease all executive bonuses to save money so the company could pay for a replacement initiative, the memo shows.

But Second Chance customers were not alerted to the problems until September 2003 -- after a California police officer was shot to death wearing the vest and a Pennsylvania officer was seriously wounded.

Second Chance says more than 100,000 Zylon vests it sold are in question, and the government said it bought at least 40,000.

In the interim, the Secret Service paid $53,000 in 2002 to Second Chance for body armor, enough to equip the president and the security detail that protects him and other VIPs, federal procurement records show.

Legal professionals and government officials familiar with the inquiry confirmed Westrick's account about the Secret Service and Bush. They said the criminal investigation is in addition to a Justice Department lawsuit filed last summer that accuses Second Chance and Toyobo of fraud. The officials spoke only on the condition of anonymity, citing grand jury secrecy.

Robert H. Skilton, Second Chance's lawyer, did not return calls to his office last week. Some of the company's non-Zylon assets have been sold and others are in bankruptcy.

President Bush throws out first pitch at a 2001 World Series game. He was likely wearing some type of body armor.