At least 17 girls have died after a fire broke out in a school dormitory in northern Thailand, local police said Monday. Officials have launched an investigation to determine the cause of the blaze that left two others missing and five injured.

The fire broke out late Sunday when most of the girls, under 13 years of age, were sleeping at their dorm at the private Pitakiatwittaya School, a Christian elementary school in Thailand’s northern Chiang Rai province, Police Captain Kachornsak Pongthit said, according to CNN. Firefighters rescued 20 girls, Sawang Momdee, chief of Chiang Rai’s fire unit, reportedly said.

“It is still very chaotic here,” the school’s manager Rewat Wassana told CNN. “We are in the process of identifying bodies, none of the parents can claim their children’s bodies yet,” he added.

A Chiang Rai provincial official told Agence France-Presse (AFP) that the privately-run school houses girls aged between six and 13, mostly from the deprived local hill tribes.

“There were 38 students inside the dormitory when the fire broke out. Some were not yet asleep so they escaped,” Arkom Sukapan, the province’s deputy governor, told AFP. “But others were asleep and could not escape, resulting in the large number of casualties.”

The two-storey school was seen engulfed in flames as firefighters worked to douse the fire, BBC reported, citing images taken by local media. The bodies of the deceased were reportedly taken to a local hospital for identification.

The school has reportedly been running for about five years and about 60 percent of the students are children from economically backward backgrounds from surrounding villages, and had been getting free education and accommodation from the Christian charity.