BEIJING - POLICE in northern China have detained three school officials after 11 schoolgirls died of carbon monoxide poisoning from using a charcoal heater in their dormitory, state media said.

A dozen fourth-grade girls were found dead on Tuesday morning at the Duiziliang Middle School in Yulin city in Shaanxi province. Eleven died and the sole survivor, 11-year-old Cai Maomao, remained in a coma, newswires said.

Police took into custody the school principal, deputy principal and a teacher in charge of class business, sources said late on Thursday. It did not say whether the three were formally under arrest or what charges they might face.

In addition, the deputy head of the county was fired from the local Communist Party ruling committee, and the education bureau director also was removed from his job, sources said.

The incident is still being investigated by local police, but they believe a quilt fell on a stove during the night, igniting coal stored under a bed, which poisoned the students, the report said.

The sole survivor, Cai, was in stable condition, and she has been able to cry and show pain, sources said, indicating she was not in the deepest kind of coma.

The families of the dead students have each been given 200,000 yuan (S$44,000) in compensation, sources said.

Carbon monoxide detectors are not required in schools in China, though the Education Ministry last year asked schools that can afford them to install detectors if they burn coal for heating.

Yulin city plans to invest 200 million yuan to upgrade the heating in 381 rural primary and middle schools, the report said. -- AP