Eleven girls died of carbon monoxide poisoning at a school in northern China's Shaanxi province, an education official said Tuesday evening. A news report said the girls had lit a fire to keep warm. A dozen girls were found poisoned Tuesday morning at the Duiziliang Middle School in Yulin city, said an official with the Yulin Education Bureau, who gave her family name as Fan. She said 11 girls were confirmed dead, with another being treated at a hospital. Fan, reached by phone, said she had no further details. The Xinhua News Agency said Tuesday the 11 girls died Monday after lighting the fire to keep warm. The report said the 12th girl was in serious condition. Xinhua did not say if the room was a classroom or a dormitory. The report also did not give the ages of the girls or other details. It said the provincial vice governor had arrived to help investigate the case.