Over 40 students were hospitalized on Friday following a gas leak at the laboratory of a school in Tiruvottiyur. Officials have not yet identified the cause of the leak.

According to police, the leak occurred at Victory Matriculation High School’s chemistry laboratory. When students in some classrooms were exposed to the gas, parents and relatives gathered in the premises.

As a number of students reported breathing difficulties at 2.45pm, they were transferred to a nearby hospital. “Most of the students admitted were girls. Only one boy was admitted. All students are stable. By 9 p.m., most of the students had been dismissed. Only five girl students are under observation,” said Manosh Kumar, doctor at Tiruvottiyur Government Hospital.

“The students cannot point to a particular gas. They said they experienced an odor and shortness of breath. But the saturation level was normal. Of the students who were taken to the hospital, only one boy was said to have been exposed to the gas,” he said.

Chennai City Health Officer Jagadeesan said all the students were stable and no injuries had been reported. “Tamil Nadu Pollution Control Board (TNPCB) officials have visited the school to check what went wrong. National Disaster Response Force (NDRF) and State Disaster Response Force (SDRF) are also monitoring the situation,” he said.

Officials have not yet determined the cause of the gas leak. The police, the Revenue and the Tamil Nadu Fire and Rescue Service are investigating.

Arumai Raj, a relative of one of the students, said the children had reported similar smell for the past two days but the school management did not take it seriously and the situation worsened on Friday. Nazar Khan, another relative of a student, said many students had also visited other private hospitals after the incident.

Greater Chennai Corporation (GCC) officials visited the locality to help and evacuate residents in case of an emergency, Jagadeesan said.

Two students were admitted to Government Stanley Medical College Hospital. They came in with very mild respiratory problems due to inhalation of the unidentified gas, the doctors said. They underwent tests, including X-rays, and were seen by the head of respiratory medicine. Both are stable now, they added.