The 165 students of the junior middle school in Tianshui City are at four hospitals, with 90 of them under less intense medical observation, an official statement said today.
The government said 412 students participated in the drill yesterday, which used smoke guns to simulate fire.
Many of them began to cough and vomit after inhaling the smoke, state-run Xinhua news agency reported.
An expert panel dispatched by the National Health and Family Planning Commission arrived in Tianshi early today to assist in the treatment.