Law enforcement sources tell us Mike died Monday in his hometown of Westbury on Long Island. We're told the cause of death is pending toxicology, but cops don't believe there was any foul play.

Mike was on the Style Network show from 2010 to 2012 ... when Olivia frequently butted heads with Tracy DiMarco, Mike's ex-gf.

Mike and Olivia weren't dating when he died, but she was clearly upset by the news.