Inmates in a prison in southeast Turkey set beds and blankets alight, starting a fire that killed 13 prisoners, authorities said Sunday. Prime Minister Recep Tayyip Erdogan said the fire affected a ward housing 18 inmates in the prison in the mostly-Kurdish city of Sanliurfa. He said some inmates set their bedding on fire following a fight that broke out inside the ward late on Saturday. It was not immediately clear if the victims had died of burns or from asphyxiation. Authorities said five of the inmates were hospitalized for smoke inhalation but none was in serious condition. The Sanliurfa prison holds some 1,000 prisoners. Erdogan said he would also order an investigation into the possibility that the ward may have been overcrowded. "I have been told by the governor that the ward's capacity may not have been suitable to house 18 people," he told reporters before his departure to Mexico to attend a Group of 20 summit meeting. Meanwhile, police used pepper gas to disperse families and protesters who attempted to make their way through a road block to reach the prison, the state-run Anadolu Agency reported. The situation at the prison was calm on Sunday and Guvenc said prison authorities would grant increased visiting time for families concerned about their loved ones.