The men are charged with supplying drugs to athletes and sports stars

On Thursday a US federal grand jury charged the group with providing banned substances to elite athletes and professional sport stars.

The men - two coaches and the president and vice-president of a San Francisco laboratory - were released until a hearing later this month to set bail.

The charges follow a six-month investigation into the case.

The court documents name Greg Anderson, personal trainer of the US baseball star Barry Bonds, Ukrainian track and field coach Remi Korchemny, Balco laboratory owner Victor Conte Junior - a former rock musician - and his Vice President James Valente.

But the documents do not name any of the performers - who include track and field athletes, as well as baseball and American football players - suspected of using banned drugs.

Korchemny coaches British sprinter Dwain Chambers, who will have a hearing into his positive test for the previously unknown steroid THG next Tuesday.

Laboratory

According to the indictment, steroids were distributed to athletes on six different occasions between December 2001 and September 2003.

BBC sport correspondent Harry Peart says Balco came under suspicion following the discovery of THG, a drug which had been specifically designed to avoid drug testing procedures.

The US Anti-Doping Agency had already named the laboratory as a possible source of THG after receiving a used syringe containing the steroid from an unnamed coach.