MONROE COUNTY, Fla. – A 28-year-old man held at the Monroe County Detention Center in Key West died late Friday night, police said.

The Monroe County Sheriff's Office reported doctors pronounced Michael Gunderson, a commercial driver, dead at the Lower Keys Medical Center.

The deputy "saw Gunderson laying on the floor of his cell with a blanket on top of him," a Monroe County spokesperson said in a statement.

"The deputy opened the cell door to tell Gunderson to get back onto his bunk. At that point, the deputy saw Gunderson's hands were clenched."

Gunderson was alone in the cell and appeared to be having a seizure, according to authorities. Records show he was being held for possession of cocaine, marijuana, drugs that require a prescription and drug paraphernalia.

The Florida Department of Law enforcement was investigating his death.