NEWPORT NEWS, Va. (WVEC) -- A Newport News inmate on work release has passed away.

According to the Sheriff's Office, Melvin Stanback, Jr., 53, was found unconscious by a co-worker. The co-worker left the work site to get over-the-counter heartburn medication and a soft drink for Stanback.

Police were immediately called, according to the worker.

CPR was preformed on Stanback until medics arrived. He was taken to Sentara CarePlex in Hampton where he died.

The Sheriff's Office said it appears Stanback died of natural causes, but a medical examiner will make the final determination.

Stanback had been in the work release program since the end of June, and he was serving time on habitual offender and DUI convictions.

The Hampton Police Department and the Newport News Sheriff's Office are conduction a death and internal investigation, as required by protocol.

No further information has been released.