At least 35 people were killed and 16 were injured after the roof of a stepwell in a temple complex collapsed in central India, a local government official said on Friday.

The incident occurred in the central Indian city of Indore after a concrete slab covering the roof of a stepwell in a temple complex collapsed, crushing devotees who had gathered to celebrate the Hindu festival of Ram Navami on Thursday, officials said.

Stepwells are a common feature across India, built hundreds of years ago, many of them ornately decorated, with access to a body of water through stairs and niches.

“The stepwell was covered, but the slab covering it collapsed because of the crowd and extra load on it,” Madhya Pradesh Chief Minister, Shivraj Singh Chouhan, the central Indian state where Indore is located, told reporters late on Thursday.

At least 75 army and rescue personnel worked through the day to remove debris, using ropes and ladders to pull out people who had fallen into the well, local media reported.

“We have rescued 18 people, 35 have been found dead and 16 are injured,” Ilayaraja T, a top local government official, told Reuters.

Prime Minister Narendra Modi expressed condolences and announced compensation for the dead and injured in the incident.