Drugs were found in Mark 'Bomber' Thompson's converted warehouse after a months-long investigation into an alleged trafficking syndicate, a source has confirmed.

But police are yet to establish if the AFL legend played any part in the alleged drug dealing operation.

Thompson presented himself to police on Tuesday, and was arrested for a formal interview, but was released without charge that afternoon.

Chief Commissioner Graham Ashton confirmed Thompson's arrest and release, but would not comment further. "The investigation's still to run its course," he said.