DMX Cancels Tour Dates Due to 'Medical Emergency,' Friends Fear Relapse

DMX is pulling the plug on several tour dates, and his people say it's because of an unspecified medical issue.

X was supposed to do a show Tuesday night in Santa Ana, CA ... but the venue informed ticket holders the show had been canceled due to a "medical emergency."

According to our sources, his Wednesday show in Los Angeles, as well as a Thursday gig in San Diego will also be postponed. We're told several people in DMX's inner circle have been concerned about his health this week.

Many fans thought he was a little off the rails during his Brooklyn show last weekend, where the Ruff Ryders reunited. We're told X was indeed drinking heavily that night.

He's battled substance abuse in the past, and friends fear a relapse.