CALCUTTA - At least 19 people have been killed and over a dozen critically injured in a fire that broke out early on Wednesday morning at an illegal market in the eastern Indian city of Calcutta.

It took three hours to contain the blaze, but rescue operations are ongoing. People may still be trapped in the old multi-story building that housed the paper and plastic Surya Sen Market in the crowded Sealdah district of the city, BBC News reports.

Toxic gases were released from the flammable materials present in the building, which hampered rescue efforts.

Initial reports suggest a short circuit may have caused the fire in an eatery on the first floor, but Mamata Banerjee, the Chief Minister of West Bengal, has hinted at a possible sabotage, according to the Hindustan Times.

"Who knows that some people deliberately set the place on fire with an ulterior motive. We have ordered an inquiry. The Calcutta Municipal Corporation, the fire department and the police will jointly conduct the inquiry and submit its report in three days," Mamata was quoted as saying by The Times of India.

There are many such illegal or "unplanned" buildings in Calcutta where fire safety measures are insufficient, if not nonexistent.