A man imprisoned at a Duluth jail died Saturday after officials said he had a medical emergency.

The St. Louis County Sheriff's Office identified 29-year-old Jonathan David Polaski as the deceased. He had a medical emergency just after 1 a.m. on Saturday and officers responded to his cell and began lifesaving measures, including CPR and using an AED.

Deputies did not clarify what medical emergency occurred.

Polaski did not regain consciousness and was pronounced dead. The Minnesota Bureau of Criminal Apprehension (BCA) is investigating the death.