A fire at a nursing home in central China left at least 38 people dead, officials said Tuesday, with bodies burned beyond recognition and wheelchairs reduced to charred frames.

The fire broke out on Monday evening in an apartment building at a privately-owned old people's home in Pingdingshan, the state news agency Xinhua said.

"The bodies were so badly burned, we couldn't tell who was who," Xinhua quoted one victim's relative as saying.

Pictures posted online showed a thick column of black smoke rising from behind a petrol station near the facility.

Another displayed the blackened frame of a building, with a burnt-out wheelchair in the foreground.

"Only myself and one other roommate managed to get out," survivor Zhao Yulan, 82, who shared her room with 11 other people, told Xinhua.

The agency said the home had 51 residents and the blaze was extinguished less than an hour after it broke out.

Two of the injured were in critical condition in hospital, the work safety bureau of the central province of Henan said in a statement on its website.

The cause of the fire remained unclear, but a provincial television station quoted another resident as blaming an electrical fault.

Xinhua, citing authorities, reported that 12 staff members had been taken into police custody as part of the investigation into the disaster. Police were also searching for three additional staffers, Xinhua said.

The building was built from steel with flammable foam fillings, the state-run China News Service said Tuesday.

Enforcement of safety standards is often lax in China, with some property and business owners paying off corrupt officials to look the other way.

- 'Lonely and helpless' -

The country's vast population is ageing rapidly, with 15.5 percent aged 60 or above by the end of last year, according to official statistics.

Nursing homes are becoming more common but are often the last choice in a culture where the elderly have traditionally lived in multi-generational households.

Care workers in such facilities are often outnumbered several times over by sick and elderly residents.

Pingdingshan survivor Chen Runde, 80, told Xinhua the home had too many residents and staff "cannot attend to all of us".

"We cannot find an attendant once night falls," he was quoted as saying.

The home was set up by a local farmer and the residents were mostly old villagers whose children had sought jobs far from home as migrant workers, it added.

The incident "highlights pain in ageing China", Xinhua said in a commentary, with care and services for the elderly still severely lagging in the country.

"Urbanisation has attracted more young people to towns and cities, leaving their old parents and children in their rural homes," it said.

"Some have no other choice but to live in poorly equipped nursing facilities... for the rest of their life.

"Instead of feeling lonely and helpless, the elders deserve a safe and comfortable place to live out their later years."

In 2013 11 nursing home patients burned to death in the northeastern province of Heilongjiang after one of them set the building on fire in a row over money.

In February this year a worker in Hunan province killed three people and injured another 15 when he attacked residents and staff at a nursing home after a row with its owner.

More widely, China has a dire industrial safety record, with accidents and fires common.

A nine-year-old boy was detained in February after a shopping mall inferno killed 17 people in Huidong in the southern province of Guangdong. Police said that blaze was "caused by a boy playing with fire at the mall".

A fire at a poultry plant in the northeast of the country killed 119 people in 2013.

Reports at the time said that managers had locked doors inside the factory to prevent workers from going to the toilet, leading to the high death toll.