Some students of a high school Tiruvottiyur, Chennai fell ill due to a suspect chemical leakage on the premises, and at least three of them were hospitalized, police said Friday.

A National Disaster Response Force (NDRF) teams deployed to determine the cause of the incident, said the exact cause was not known.

Preliminary investigations by the police showed that no gas came from the school lab.

Some students complained of breathing difficulties and eye irritation, while others felt a sudden sense of nausea that triggered a panic at school.

“Some of us had to rush out of the classroom to get fresh air. Even our teachers had found it difficult to breathe. Some students even fainted and our teachers revived them,” a student later said, adding that she felt nauseous.

As many students complained of anxiety, management had to call ambulances and take the students to hospital. Even parents who showed up at school admitted their children to a government hospital where many were treated as outpatients. Police said it was not clear whether the leak occurred from the school or originated from the nearby location of a chemical plant. The condition of three students admitted to the Stanley Government Medical College Hospital here was said to be stable, police said, adding that nearly 30 students complained of restlessness and throat irritation.

“Our team evaluated the chemistry lab and checked the air conditioning unit, we did not smell any gas or leakage from the AC unit. We cannot say the exact cause of the gas leakage. We are yet to ascertain it,” NDRF Commander AK Chauhan, told reporters later .

State government officials also visited the school to inquire about the cause of the suspected chemical gas leak.