A local drug watchdog has launched an investigation into a hair care company in Zhejiang province after its products for the Singapore and Hong Kong markets were found to contain a banned chemical, Xinhua News Agency reported on Wednesday.

The Zhejiang food and drug administration is investigating Zhangguang 101 Co Ltd after some of its products for Singapore and Hong Kong were found to contain Minoxidil, which is a banned ingredient for cosmetic products.

Minoxidil was first used to treat high blood pressure, but clinical studies found that it also stimulated hair growth and slowed balding. However, it can also have a number of potentially serious side effects, including chest pain, fainting, accelerated heart rate and severe allergic reactions.

All the suspect products have been pulled from shelves in Singapore and Hong Kong.

Zhangguang 101 said the investigation was a "normal process" for the administration in such cases and stressed that the tainted products were only for export sale.

"So far, no products in the mainland market have been found to contain the banned chemical," said an announcement on the company's website.

The company claims that some alcohol solution that contained Minoxidil was accidentally mixed with ordinary alcohol and that it did not add the banned chemical to the products deliberately.

"All our products are made from traditional Chinese medicine," a company secretary surnamed Zhang told China News Service.

However, as early as March, hair cream products of Zhangguang 101, on sale in Guangzhou, capital of Guangdong province, were found to contain the potentially cancerous toxic chemical lentine.

"If the chemical is absorbed by the skin it may cause damage to the kidney and liver," Guo Yuhua, spokesman of the Guangzhou food and drug administration, warned at the time.

Zhangguang 101, founded in 1987, has fixed assets worth more than 1 billion yuan ($149 million) and its products are sold in 65 countries and regions, with 10 million consumers around the world, according to the company's website.