An Islamic boarding school in Malaysia caught fire Thursday, killing at least 23 people—most of them teenage boys who screamed for help from barred windows but were not saved in time. The blaze began at about 5:40 a.m. in one of the dorms, where most of the students were sleeping. Two teachers also died in the fire near Kuala Lumpur. The dorm only had one entrance, Reuters reports. “The building was surrounded by metal grills that could not be opened from the inside. The students, after realizing there was a fire and heavy smoke, tried to escape through the window,” Fire Department Operations Deputy Director Soiman Jahid said. “But because of the grills, they could not escape.” The blaze was likely caused by a short circuit, he said.