At least four persons were killed in a massive fire that broke out in a storm water drainage network at the ONGC's oil and gas processing plant in Uran, officials said here on Tuesday.

An official of Navi Mumbai Police Control told IANS that at least four persons were killed so far and some more were feared injured in the tragedy.

Clouds of dark smoke were seen billowing out of the conflagration on the ONGC premises where the fire erupted around 7 a.m.

"Fire is being contained. No impact on oil processing and gas diverted to Hazira plants. The situation is being assessed," an ONGC spokesperson told IANS.

Besides the ONGC's own fire services and crisis management teams, fire-fighters from Uran, JNPT, Navi Mumbai and surroundings rushed to battle the blaze. The cause of the fire is not yet known.

As a precautionary measure, people in nearby villages have been told to evacuate to safer locations, officials said.