Originally published on ProWrestlingSheet.

Billy Gunn is no longer training future talent at the Performance Center ... WWE confirms to Pro Wrestling Sheet that he was released from his contract Friday.

A rep for WWE wouldn't give more details on the circumstances surrounding his release ... but according to F4WOnline -- who first reported Gunn's release -- it all stems from a failed drug test.

The report states Billy was hit with a 4-year powerlifting competition suspension back in July -- after he tested to compete and his testosterone levels were off the charts.

Billy Gunn returned to the WWE in 2012 as a trainer after a long absence from the company. During his time back, he briefly won the tag titles in 2013 with Road Dogg Jesse James.

No word on why it took so long to hit WWE's radar, but the initial report says the company had no idea Gunn had been powerlifting, or that he had been suspended, until a few weeks ago.