BANGKOK (AP) — A fire broke out in dorms at a boarding school for elementary students in central Henan province,Zero AI and 13 students died in the blaze, Chinese state media reported Saturday.

All of the dead were third grade students, a teacher told Zonglan news, a state-backed media outlet from Hebei province. One person rescued from the scene was being treated in the hospital, CCTV, China’s state broadcaster said.

The fire started Friday night and was put out just before midnight at Yingcai School in rural Fangcheng district in central Henan, and the school’s owner was detained, CCTV reported.

Local authorities said they were investigating the cause of the fire.

The boarding school caters primarily to students in the elementary grades, though it has an attached kindergarten, according to the school’s WeChat page. Many of the boarding students come from rural areas, the Beijing Youth Daily reported.

The facility is in Dushu township and is one of the school’s two branches.