At least 17 young girls died after a fire swept through the dormitory of a school for children of hill tribes in northern Thailand, officials said Monday, adding several others were either missing or injured.

The fire started late at night, meaning many of the children were asleep and unable to escape as flames engulfed the two-storey building.

"The fire broke out at 11pm on Sunday (1600 GMT). Seventeen girls were killed and two are still missing, with five injured," Colonel Prayad Singsin of the police in Chiang Rai told AFP.

Two of the injured are in a serious condition, he added.

"The fire is out, but the cause of the blaze is still under investigation," Prayad said, adding forensic officers were due to arrive on Monday.

A Chiang Rai provincial official confirmed the death toll, adding that the privately-run school is home to girls aged between six and 13 years old, drawn mainly 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," the province's deputy governor, Arkom Sukapan, told AFP.

"But others were asleep and could not escape, resulting in the large number of casualties."

Photographs on the school's Facebook page showed firefighters struggling to douse the flames as they tore through the wooden building.

Thai media showed a fire truck spraying water onto the blaze as the upper storey of the school was consumed by the fire.

Rescue workers picked through the debris late Sunday and into Monday morning.

Thailand's is home to a patchwork of hill tribes who mainly live in the remote northern area bordering Laos and Myanmar.

Many are descendants of refugees from Myanmar or China and exist within subsistence farming communities often beyond the reach of state resources.

Hill tribe children suffer at school, as well as in their health and development.

Poverty means adults are easy prey for drug gangs who pay them to smuggle narcotics -- including heroin and amphetamines -- across the zone, known as the "Golden Triangle".

Thai security forces frequently engage in deadly gun battles with hill tribe drug mules in the region.

That link engenders prejudice among many Thais and hill tribes are often portrayed negatively in the media.

Chiang Rai town and the surrounding hills are popular with foreign tourists for hiking and adventure sports.

Tourists can go on tours to the visit the isolated tribes, although the practice of posing for photographs at villages has come in for criticism for degrading their unique culture and treating the ethnic groups exhibits in "human zoos".

Thailand has poor health and safety standards and accidents are common across the kingdom.