The family of a former U.S. Marine locked up in Russia on espionage charges say they’ve grown concerned for their loved one’s whereabouts after hearing nothing from him for several days. Paul Whelan, who was sentenced to 16 years for crimes which he denies, was moved to the hospital at a prison in Russia’s Mordovia region, staff at the penal colony said. But Whelan’s brother David Whelan told Reuters that staff said Paul was moved there on Nov. 17, and Paul didn’t mention any such move when he last spoke to family on Nov. 23. The family hasn’t heard from him since and says he’s always mentioned moves to the prison hospital in the past. “Paul was not complaining of any health conditions that required hospitalization, so has there been an emergency?” David said. “Is he unable to make calls? Or is he really still at [the penal colony] but he’s been put in solitary and the prison is hiding that fact?” David added that American and Irish diplomats who visited Paul the day before his purported move said Paul had appeared healthy.