Din Thomas (Pictures) was arrested Tuesday in Port St. Lucie, Florida, for running in his local gym what a police spokesman called "illegal cage fighting" matches.

The TCPalm reported that Thomas faces a felony prohibited-competitions charge after police entered his training studio and watched two men fighting in an "octagon-shaped ring" before roughly 150 spectators.

"At the end of the day, he was having a professional mixed martial arts match that was not licensed through us," Sam Farkas, a spokesman for Florida's Department of Business and Professional Regulation, told the TCPalm. "It was a case of unlicensed activity."

Sherdog.com confirmed the arrest with a representative of Thomas' American Top Team camp. According to ATT, Thomas was in the process of posting a $10,000 bond to obtain his release from jail.

Thomas, a veteran lightweight currently competing in the UFC, lost his most recent bout on Sept. 19 to Kenny Florian (Pictures) in the main event of a UFC Fight Night card. He injured his knee in the match before succumbing to a rear-naked choke.

Prior to the Florian loss, Thomas was on a three-fight winning streak in the UFC.