The medical examiner's office will determine how a woman died while in custody at the Irving jail early Sunday.
Irving police said 48-year-old Teresa Giles was found unresponsive in her jail cell at about 5:08 a.m. by detention center staff.
Giles was transported to Baylor Scott & White Medical Center – Irving, where she was pronounced dead at about 5:52 a.m.
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Police said Giles had been booked into the jail just before 8 p.m. Friday on a charge of possession of heroin and possession of drug paraphernalia.
Investigators said there was no obvious sign of trauma, and the cause of death is unknown.
Results from an autopsy by the medical examiner's office are pending.