At least five people were killed and more than 13 people were injured in a building collapse in Kanpur on Wednesday. The structure in Shivrajpur area fell after an explosion believed to have been caused by an ammonia gas leak. However, investigators have yet to confirm the chronology of the events. Nine people are still trapped under the rubble, reported NDTV.

“Prima facie, it appears that the blast took place owing to a leakage in an ammonia gas tank at the chiller plant and this probably led to the cold storage building’s collapse,” a police official told The Times of India. “However, experts from horticulture department have been summoned to ascertain the exact cause.”

More than 24 people were working inside the cold storage building when the incident took place. Fire brigade officials and National Disaster Response Force teams are present at the site to pull out people still strapped under the debris. The district magistrate and senior police officials are also overseeing the rescue operation.

The local administration has ordered a probe into the incident. The Katiyar Cold Storage, which is owned by a local resident Vishwanath Singh Katiyar, did not have the right licence for the building, the newspaper reported, quoting unidentified locals.