A fire at Changfeng Hospital in Beijing has killed 29 people. Most of the deceased were reportedly patients. A nurse, medical worker and relative patient also died in the fire. At least 21 people were hospitalized in critical or serious condition, The New York Times reports. The average age of hospital patients who died in the fire was 71.

At a press conference on Wednesday, officials said that the “sparks generated during renovation works had ignited paint stored on site,” the BBC reports. At the time of report, 12 people have been detained by police, including the director and deputy director of the hospital, as well as the head of the firm overseeing the renovation. They are being investigated for possible violations of safety management regulations.

Social media posts showed patients jumping out of windows to flee the building. Meanwhile, a talking drone urged trapped patients to “stay calm and wait [to be] rescued,” the BBC reports.

Firefighters reportedly evacuated about 70 people and extinguished flames within an hour of arriving.

“We feel deeply responsible and guilty,” said Li Zongrong, a deputy district mayor of Beijing’s Fengtai district said in a statement. “I would like to express our deep condolences to the victims, sincere greetings to the families of the victims, the injured and their relatives, and apologies to the people of the city.”

The fire prompted public safety officials across China to conduct impromptu inspections of hospitals and senior care facilities to ensure that evacuation routes were not obstructed, The New York Times reports.

At the time of reporting, the western section of the hospital is still caring for patients but is not receiving new ones.

Mackenna Moralez is the associate editor for the facilities market.