Real estate developers are investigating a type of wood flooring produced by a Shanghai-based company, after claims it was releasing excessive amounts of a carcinogen.

Anxin floors, produced by A&W (Shanghai) Woods Co Ltd, are said to have been used in several real estate projects in Shanghai, Guangzhou, Chongqing and Chengdu, and by several leading property developers, including Vanke and Longfor.

Shanghai's quality authorities are also testing the flooring. Their findings are expected later this week.

Last week, Li Xiaoyan, who said she was a deputy editor-in-chief for a construction materials magazine, claimed on an online forum that Anxin flooring was substandard and contained excessive levels of formaldehyde. She said the formaldehyde the flooring releases was five times higher than the country's standard.

She also said the flooring would last just two years. Her post said that since 2008, A&W had provided flooring for up to 10 real estate developers.

China Vanke, the country's largest publicly traded property developer, told Xinhua news agency yesterday it was investigating potential problems in the wood flooring. The group has begun quality checks on its stock of flooring materials and the results will be published at the end of the month.

Tan Huajie, secretary of China Vanke's board of directors, said it purchased and used wood flooring made by A&W for 29 projects in 16 cities, including Shanghai, Beijing and Guangzhou.

Yu Liang, president of China Vanke, said the wood flooring involved was worth 130 million yuan (US$20.7 million) and that the company would take responsibility if there were any quality problems, Xinhua said.

Some other real estate developers, including Longfor, have also begun investigations.

Meanwhile, residents living in houses that have Anxin flooring installed have published several posts in online forums, asking how formaldehyde affects human heath. Some lawyers have said if the residents launch a lawsuit against the real estate developers and A&W, the compensation could be huge.

Hui Xiaowei, vice president of A&W, denied the allegations last Friday, saying at a press conference that all the wood flooring sold by the company was up to national standard.

A&W has two plants in Qingpu District. Shanghai-based China Business News reported yesterday that employees told it the quality of Anxin flooring "varied."

They reportedly said people should avoid buying A&W's cheap flooring as it was "harmful to human health."