Eleven persons died in northeastern Delhi’s Mustafabad area after a four-storey residential building collapsed on Saturday, The Hindu reported.

Eleven others were injured, the newspaper reported. The rescued persons were taken to hospital.

Teams from the National Disaster Response Force, firefighters and the Delhi Police were involved in the rescue operation, The Indian Express reported.

The police said they were informed about the building collapse at about 3 am following which a team was sent to the location.

It was unclear what had caused the structure to collapse.

Mohsen Shahidi, the deputy inspector general of the National Disaster Response Force, told PTI that the incident was what the agency describes as a “pancake collapse”. It is “one of the most dangerous types, where the chances of survival are very low,” Shahidi was quoted as saying.

“However, we remain hopeful that there are lives to be saved and are continuing our search operations,” he added.

Shahidi explained that the debris must be cleared carefully because of the high density in the area. Additionally, the lack of space had restricted the use of heavy machinery, adding to the challenges faced during the rescue operations.

Chief Minister Rekha Gupta expressed her condolences, adding that a probe had been ordered into the incident and that action will be taken “against the culprits”.

The Delhi Disaster Management Authority, the National Disaster Response Force and the fire services, among other agencies, were “continuously engaged in relief and rescue operations,” Gupta said on social media.

“Arrangements have been made for proper treatment of all the injured,” she added.