A 49-year-old inmate at the jail in Shediac has been found dead, according to the Department of Justice and Public Safety.
Staff at the Southeast Regional Correctional Centre called 911 when the man was found unresponsive in his cell, the department said in a statement.
"Despite efforts to revive the man, he died at 6:35 p.m.," a news release said.
An automated external defibrillator was used and paramedics were there to perform resuscitation efforts.
Coroner Services and the RCMP are investigating the death, and correctional services will conduct an internal review.
The department said the inmate's name will be released once next of kin are notified.
Department spokesperson Danielle Elliott said no other details are being released at this time.