Selangor fire and rescue department director Norazam Khamis said the incident happened at 1.20pm when the Year 5 pupils were conducting experiments in the school laboratory.

He said the four students were sent to Shah Alam Hospital and all of them were reported to be in stable condition.

He said fire rescue personnel were sent to the school to ensure the school was safe and the environment free from leaking gas.

In a separate incident, Norazam said an 18-year-old teenager was injured in a gas explosion at a restaurant in Jalan Bidara, Saujana Utama 3, Sungai Buloh, near here, at 12.30pm yesterday.

He said a cooking gas leak was believed to have caused the explosion and a small fire which destroyed 30% of the premises.

The victim was treated for burns at the Puncak Alam Hospital, he said.