Ziroom responded to the incident on Weibo, China’s Twitter-like service, on Saturday, saying the company would cooperate with law enforcement and communicate with the family accordingly.

The Beijing News reported on Monday that Zuo Hui, the board chairman of Ziroom’s parent Beijing HomeLink Real Estate Brokerage and a shareholder of Ziroom, said on his WeChat Friend Moments that the company would take all criticism and shoulder all responsibility. This could not be independently verified by South China Morning Post.

Ziroom said on its official WeChat account that with immediate effect, all of its flats being rented out for the first time would be unlisted temporarily, and only returned to market if they passed air quality tests.

Tenants of newly listed Ziroom flats who moved in from June 1 can apply for a free air quality check and, if the quality is substandard, Ziroom has offered a refund, a free switch to another room, free air quality control measures or an air purifier for 90 days.

News of the case, reported in Thepaper.cn, heightened public concerns on the back of other reports of excessive levels of formaldehyde in paint and other “poisonous” substances used in building and decorating materials in homes for rent across China.

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Wang’s widow said her husband had started working for Alibaba, which owns the Post, in April, Thepaper.cn reported. He left his family in Beijing and started renting a flat in Hangzhou on May 8.

On July 6, he travelled back to Beijing, where his family took him to hospital as he looked unwell.

On July 10, he was diagnosed with acute myeloid leukaemia (AML) at Chaoyang Hospital in Beijing and died on July 13.

According to the report, Wang’s wife provided a health assessment which showed no abnormalities during a check-up in January.

After Wang’s death, his wife hired the Hangzhou Be-Top Testing Service, a company that measures air quality, to test the air in the flat.

The company found that while benzene, methylbenzene and total volatile organic compound levels met national standards, there was an excessive concentration of formaldehyde in the flat, at 0.132 milligrams per cubic metre, compared to the recommended limit of 0.1 milligrams per cubic metres.

Neither Ziroom nor Wang’s wife responded to requests for comment.

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Nanjing-based doctor Qin Ruomeng said there was no definite connection between high levels of formaldehyde and AML, although some epidemiological studies showed that long-term contact with formaldehyde was associated with respiratory tumours. AML has been linked to high levels of benzene.

Such cases may be legally difficult to win, according to Zhou Kai, a civil lawyer from Nanjing-based Jiangsu Tianzhe Law Firm, since no definite link can be proven.

A search of China Judgments Online, an official site which collates legal data, turned up 25 lawsuits involving AML and formaldehyde, with most cases lost.

There have been many media reports of discomfort caused by high chemical levels in the past, many of them with Ziroom flats.

On August 5, the Beijing Times reported that a Ziroom renter in the capital felt nauseous because of excessive formaldehyde levels. On August 20, Sina.com reported a Beijing renter claimed excessive chemical levels caused red goosebumps to break out all over his body.