A former New York Mets clubhouse employee pleaded guilty Friday to distributing steroids to major league players, and is co-operating with baseball's steroids investigation.

Kirk Radomski, 37, pleaded guilty to felony charges of distributing steroids and laundering money, charges that carry sentences of up to 25 years in prison and a $500,000 US fine.

"This individual was a major dealer of anabolic steroids, including human growth hormones, whose clientele was focused almost exclusively on Major League Baseball players," prosecutor Matt Parrella said outside court, according to the San Jose Mercury News.

Parrella declined to name Radomski's clients.

The story was first reported by the New York Daily News.

Radomski, who worked for the Mets from 1985-95, has agreed to co-operate with the MLB investigation led by former U.S. senator George Mitchell.

"We look forward to working together with federal law enforcement toward our shared goal," Mitchell said in a statement.

Radomski dealt human growth hormone, deca-durabolin and testosterone, among other drugs, according to a search warrant affidavit obtained by the Mercury News.

The warrant had some information blacked out, including what appeared to be the names of players.

According to the warrant, Radomski became a major source of drugs for baseball players after federal investigators shut down Bay Area Laboratory Co-Operative (BALCO) in San Francisco.

The case is being handled by the same federal investigators who netted guilty pleas from BALCO founder Victor Conte and Barry Bonds's personal trainer, Greg Anderson, among others.

Howard Johnson, a Mets infielder in the 1980s and currently their first-base coach, remembered Radomski.

"He was a clubhouse kid, one of several, one of the kids that were there," Johnson said before the Mets played at Washington on Friday night.

Former Mets pitcher Ron Darling, now a team broadcaster, said he didn't remember Radomski.

Mets spokesman Jay Horwitz said equipment manager Charlie Samuels would not be available for comment.

"We were surprised and disappointed to learn of the guilty plea today," the Mets said in a statement.

"The conduct in question is diametrically opposed to the values and standards of the Mets organization and our owners. We are and always have been adamantly opposed to the use of performance-enhancing drugs and continue to support MLB's efforts to eradicate any such use in our game."