SHENYANG -- Thirty-seven students were admitted to hospital after a leak of poisonous gas from a nearby chemical storehouse in northeast China's Liaoning Province, hospital sources said on Thursday.

Three students, including one who is seriously ill, were still under observation in the First Affiliate Hospital of China Medical University on Thursday morning, while the 34 others have been discharged.

The leak happened at 9:00 p.m. on Wednesday at Liaoning Petroleum and Chemical Storehouse in Dongling District in the industrial city of Shenyang, investigators said.

The lid of a container broke off the container after the temperature rose, according to investigators, but they gave no other details.

The vocational school, which is next door to the storehouse, has about 300 students.