A fierce fire ripped through a hotel in the Indian city of Kolkata killing at least 15 people, police said Wednesday, with some clambering out of windows and onto the rooftop to escape.

Several people were rescued from rooms and roof of the budget hotel, Kolkata police chief Manoj Verma told AFP, after the fire broke out on Tuesday evening.

“The death toll has risen to 15, including two children and a woman,” said Verma, adding an investigation had been launched to find out what triggered the blaze. “The hotel turned into a gas chamber and it appears that many people suffocated to death.”

The Rituraj Hotel, which had 88 guests when the fire broke out, is located in a congested business district of central Kolkata. About a dozen people suffered burn injuries and were undergoing treatment.

Building fires are common in India due to a lack of firefighting equipment and a routine disregard for safety regulations. Last year, six people were killed in a fire at a hotel in Patna in the eastern state of Bihar.

The Press Trust of India news agency, which filmed images of soaring flames from the Kolkata building, reported that “several people were seen trying to escape through the windows and narrow ledges of the building”.

Kolkata’s The Telegraph newspaper reported that at least one person died when he “jumped off the terrace trying to escape” the fire.

Verma said the fire had been tackled and that “cooling operations are underway”.

Prime Minister Narendra Modi offered his condolences to the families of those killed. “May the injured recover soon,” his office said in a statement.

Kolkata, a bustling metropolis of more than 15 million people, is the capital of West Bengal state, which is governed by the opposition Trinamool Congress party.