NEW DELHI (AP) — A building that was being expanded in the Indian capital collapsed Saturday, killing five people on the main floor, including four students, an official said.

The students were attending a coaching class on the first story of the building in New Delhi’s Bhajanpur area when the roof came crashing down, fire officer Umesh Garg said.

He said eight injured students were hospitalized after they were rescued from the rubble. Their injuries were not life threatening, Garg said.

He said the building was having a second floor added at the time of the collapse.

Authorities are investigating the cause of the building collapse.

Building collapses are common in India as many are poorly constructed with cheap building material, ignoring safety guidelines to cut costs.

In July last year, 14 people were killed when a dilapidated four-story building collapsed in India’s financial capital of Mumbai. Also in Mumbai, 72 people were killed when a residential building being constructed illegally collapsed in 2013.