Charlotte, N.C. ? Carolina Panthers center Jeff Mitchell, one of three players identified as having obtained steroid prescriptions, declined to comment Friday on his role in the investigation of the doctor accused of writing the illegal prescriptions.

Mitchell, punter Todd Sauerbrun and offensive lineman Todd Steussie, who now is with Tampa Bay, all were named in a CBS report as having obtained the illegal prescriptions from South Carolina alternative medicine doctor James Shortt.

Mitchell was on the field Friday for the first session of Carolina’s three-day minicamp and stopped to talk to reporters after practice. But when the subject of steroids came up, he declined comment.

The Panthers told Sauerbrun not to come to minicamp, and have acknowledged they actively are trying to trade him. But coach John Fox said there was no discussion of having Mitchell sit out the session.

“In this society you are innocent until proven guilty,” Fox said.

Several Panthers players testified this week before a federal grand jury about Shortt, The State newspaper of Columbia, S.C., reported.

Sauerbrun and Steussie were not called to testify. A lawyer for Steussie said he was cooperating with investigators, and The State reported that Sauerbrun was as well. It is not clear if Mitchell is, and the Panthers have maintained they have little knowledge of the situation.

Commissioner Paul Tagliabue said this week that the NFL security department also was investigating.