NEW DELHI — At least six people were killed when a building collapsed Thursday in northern India as workers were adding an additional floor to it, police said.

Police officer Satbir Singh said a fourth story was being constructed on the building when it collapsed in a village on the outskirts of Gurgaon in Haryana state. It was unclear whether the additional floor had been approved by authorities.

Singh said dozens of rescuers were searching for people who could be trapped in the debris.

Building collapses are common in India as builders try to cut corners by using substandard materials and as multistory structures are built with inadequate supervision or approval.

A massive demand for housing and pervasive corruption often result in builders adding unauthorized floors or putting up illegal buildings.

A collapse in 2013 killed at least 72 people in Mumbai.