Mumbai, Jul 15 (IANS): Mumbai Police Thursday registered a case against "unknown persons" in connection with the chlorine gas leak at the Mumbai Port Trust (MPT) premises that led to 100 people falling sick.

"A First Information Report (FIR) under the Environment Protection Act has been registered against unknown persons. Probe is on in the matter," said senior police inspector Rajan Bhogale of the Sewree Police Station, where the FIR has been registered.

"The charges included in the FIR are attempt to commit culpable homicide and negligent conduct with respect to poisonous substance amongst others," he added.

Efforts are still on to reduce the effect of the gas leak. "Around 14 tonnes of caustic soda and four tonnes of water have been used to lessen the effect," a Central Industrial Security Force (CISF) official told reporters here Thursday.

At least 92 people, many of them students, were taken ill after chlorine gas leaked early Wednesday at the MPT scrapyard.

According to a fire brigade official, the gas leak was noticed around 3.30 a.m. when people in the area started complaining of burning eyes, breathlessness and nausea.

An MPT spokesperson added that 141 cylinders were imported in 1997, but the importers had not taken delivery of the consignment; this had been lying in the open for nearly 14 years.

Only five cylinders had gas while 136 were empty, the official added.

Besides the MPT officials, experts from the Maharashtra Disaster Management Authority, the state-run Rashtriya Chemicals and Fertilizers and the semi-government Century Rayon companies are assisting in the relief operations.