The death toll from the fire had risen to 29 on Wednesday from 21 the previous day, making it the deadliest structure fire in the capital in at least two decades.

The dead included 26 elderly patients, a healthcare worker, a nurse and a visitor, officials said during a press conference on Wednesday afternoon.

At least 39 people were hospitalised – three of them in critical condition.

All of the injured patients had to be sent to nine other nearby hospitals due to limited capacity at Changfeng.

Twelve people, including the hospital director and the head of a construction company, have been detained by China’s Public Security Bureau for a “crime of major liability accident”, as the investigation continued.

A preliminary investigation showed that flammable paint supplies had been ignited by sparks during renovation work at an inpatient department, officials said.

Emergency crews were called to the hospital just before 1pm on Tuesday.

China hospital fire in Beijing kills 21, says newspaper

The fire was put out in half an hour with rescue work completed by 3.30pm, officials said. Seventy-one people were evacuated.

According to local media reports, the fire spread on the fifth floor of the east wing of the building, where mostly elderly and palliative care patients with reduced mobility are treated.

Changfeng Hospital, which opened in 1985, is a secondary-level private hospital with about 130 inpatients. The east wing, which focuses on intensive care, was sealed off after the fire.

Dozens of family members gathered at the front desk throughout the day on Tuesday to check on the status of their relatives, but struggled to get information on their conditions or which hospitals they had been transferred to, China Youth Daily reported.

After an official announcement at 9pm, a group requested a list of the deceased, but were told they could only file inquiries one at a time and would have to wait for the authorities to reply.

“I haven’t even got a call in the past seven to eight hours [since the fire occurred] … I wouldn’t have known it if I hadn’t read the news,” one person told a reporter.

Fengtai district had “swiftly” formed an emergency task force to confirm the status of patients, relatives and caretakers, Li said.

The task force would also “manage the fire site, patient and injury treatment, liability issues and assist in the investigation”, he said, adding that assistance would be provided to those whose family members died as a result of the fire.

The hospital was under heavy police guard on Wednesday with at least 20 police vehicles around the facility, preventing people from gathering near the site.

As police officers dispersed crowds from around the site, and later urged reporters to leave, a 61-year-old retired teacher told the South China Morning Post that he had come to pay respects to the victims of the fire.

“As an elderly person myself, I feel empathy for those affected. I could not sleep last night and stayed up past 1am. I am deeply saddened by this incident,” he said.

Nearby streets also had a heavy police presence, while fences had been put up around the charred inpatient building. However, patients with appointments and immediate family members of inpatients were still allowed to enter another building at the facility after registering.

A woman who left the hospital on Wednesday said her medical check-up had taken place as scheduled, after her doctor had escorted her into the building.

The Chinese Non-government Medical Institutions Association announced on Wednesday that it would cancel the membership of the hospital, and remove some of the association’s board members because of the severity of the incident, financial news site Jiemian reported.

A fire in 2017 killed 19 people when a building in Beijing’s Daxing district that had been converted into tiny flats caught fire.