No fewer than 29 persons have died following a fire outbreak in a private hospital in Beijing, the Chinese capital city.

The fire broke out at the East wing of the Changfeng Hospital housing in patients on Tuesday afternoon, forcing dozens of people to evacuate, state media CCTV reported.

Amateur video from the scene showed people escaping from windows with bed sheets tied together and improvised as ropes. Others perched on the air conditioning units positioned on the exterior of the building while waiting for help.

The deceased include 26 patients and other victims, according to local media. A total of 71 patients were rescued by emergency crews who have since extinguished the fire.

A total of 39 people are being treated for injuries, three of them in critical condition, officials said. 

Twelve people, including the hospital head, her deputy, and the head of the construction crew were detained by the authorities over the incident.

The cause of the fire is under investigation but officials say they believe it originated from welding sparks from work being done in the hospital’s inpatient wing.

The fire is one of the most deadly in Beijing in recent years, surpassing the toll from a fire in 2017 that killed 19 in a cramped two-story building in Daxing district in the capital’s southern suburb.