A Sacramento County male inmate was pronounced dead Tuesday after he was found unconscious in his cell.

The 55-year-old inmate had been incarcerated at the downtown Main Jail since Sunday on “a commitment warrant for a theft-related” charge, according to a county Sheriff’s Department news release.

Just before 6 a.m. Tuesday, deputies spoke to him via an intercom to begin his transfer to another “custody facility.” When the inmate did not respond, deputies entered the cell he shared with another man and found him to be unconscious.

They began to try to resuscitate him, an unsuccessful effort that continued when medical personnel summoned from outside the jail arrived.

The inmate’s body had no marks of trauma. The cause of his death is under investigation.

The Sheriff’s Department news release notes that foul play is not suspected.