U.S. prosecutors kept up pressure on Barry Bonds on Thursday by subpoenaing his personal trainer to appear before a grand jury next week but did not return an anticipated indictment against the Major League Baseball slugger. Lawyers said a federal grand jury looking into steroids in professional sports served its last day on Thursday, a deadline which prompted many, including Bonds' lawyer, to anticipate a possible indictment on perjury charges against Bonds over past grand jury testimony. The statement appeared to refer to Greg Anderson, Bonds's friend and personal trainer who was imprisoned this month after refusing to testify before the grand jury. His attorney Mark Geragos said he was released from prison on Thursday as the grand jury's term expired, but was immediately served with a subpoena to testify next Thursday before a new grand jury. Anderson has already served a short prison sentence on steroid distribution charges on evidence uncovered in the probe of the San Francisco area BALCO labs. The head of BALCO also served time in the doping scandal that tarnished some of the top names in baseball and track and field. The latest perjury investigation around Bonds centers on what he told the BALCO grand jury in 2003. His lawyer Mike Rains said the single-season home run record holder testified he never knowingly used steroids. Federal prosecutors apparently do not believe him and are trying to show otherwise. Lawyers say proving perjury is very difficult. Bonds, who this season passed Babe Ruth for second place on the all-time Major League home-run list, has never failed a steroid test, so the government has sought information from his friends, lovers and associates. This year's book about the BALCO scandal "Game of Shadows" quotes one of Bonds' lovers, Kimberly Bell, as describing him as a player who knowingly used steroids.