A St. Louis man is believed to have taken his own life while being held at the Monroe County Jail in Waterloo.

Monroe County EMS responded Monday morning to the jail for an unresponsive 39-year-old male inmate. The man, identified as Devin York, was transported to St. Anthony’s Medical Center in St. Louis County, where he was pronounced dead.

“The male subject was being held from a Waterloo Police Department arrest involving various charges and a warrant for his arrest out of Missouri,” Monroe County Sheriff Neal Rohlfing stated in a press release issued Tuesday.

York was arrested Saturday and was being held in a cell by himself, Rohlfing told the Republic-Times. He was arrested for theft, possession of a controlled substance and possession of drug paraphernalia in addition to the warrant, police said.

The Illinois State Police Investigations Division and Crime Scene Unit responded to the jail to conduct an independent investigation. The cause of death has not been released pending toxicology reports but is believed to be a suicide.

“We were requested by the Monroe County Sheriff’s Department to assume the investigation of an apparent self-inflicted injury which caused his death,” said Lt. Dave Bivens of the ISP Investigations Division. “There is no apparent foul play suspected, but we’re still looking at it as a whole to make sure.”

ISP investigators were brought in to ensure an impartial investigation was conducted, Bivens added.