SAN FRANCISCO -- Former NFL defensive lineman Dana Stubblefield pleaded guilty Friday to lying to investigators in the BALCO steroids case, making him the first football player charged in the long-running federal investigation.

Stubblefield, a three-time Pro Bowl player who testified before the BALCO grand jury in November 2003, was charged with making false statements to federal agents about his use of performance-enhancing drugs.

The charges, unsealed in federal court, allege Stubblefield lied to an IRS agent when he said he had not used steroids linked to the Bay Area Laboratory Co-Operative and denied receiving performance enhancers from BALCO founder Victor Conte.

The plea deal calls for the 37-year-old Stubblefield to spend zero to six months in prison, though U.S. District Judge Susan Illston said she is not bound by that agreement and can sentence him to up to five years. He is to be sentenced April 25.

Stubblefield and his attorney, Mike Armstong, declined to comment as they left court.

Stubblefield is the latest target in a federal investigation that has spanned five years and ensnared several elite athletes and members of the Burlingame-based steroids distribution ring, including Conte, who served four months in prison.

The biggest name was Barry Bonds, the former San Francisco Giant and baseball's career home run king. He pleaded not guilty to perjury and obstruction of justice charges and is awaiting trial.

Stubblefield played on the defensive line for the San Francisco 49ers, Washington Redskins and Oakland Raiders from 1993-03, and was the NFL defensive player of the year in 1997 while with the 49ers.

He was one of three players fined by the NFL for testing positive for the designer steroid THG, but he was not suspended because THG was not added to the NFL's banned substance list until after the tests were conducted.

According to prosecutors, Stubblefield received notice from the NFL on Nov. 10, 2003 that he had tested positive for THG, which was distributed by BALCO and known as "the clear."

Three days later, he told IRS agent Jeff Novitzky he had never used that substance, according to the charges.

"During that interview, Mr. Stubblefield stated that he never seen the substance and never ingested it," Assistant U.S. Attorney Jeff Nedrow said.

Stubblefield also admitted in court he lied when he said he never ingested the oxygen-producing drug EPO and he never dealt with Conte, who ran the BALCO steroids ring.

Nedrow also said that when federal agents raided BALCO in November 2002, they seized "documents and other information" showing Stubblefield paid Conte for performance-enhancing drugs.

Stubblefield's lies "played a material role in the investigation," Nedrow said. "It had the effect of impeding the investigation."