Authorities in Wudangshan, Hubei province, have launched a formal investigation into an allegedly illegal clinic operating as an "anti-cancer center".

A joint statement from the local health bureau, market supervision bureau and public security bureau on Monday night confirmed the launch of legal proceedings.

The findings will be promptly shared with the public, said the statement.

Earlier reports from the Beijing News alleged that the clinic falsely promoted secret cancer treatments, engaged in deceptive advertising, and hired unqualified personnel in violation of health regulations.

The clinic operated from April 18 to May 31. During that time, 15 patients reportedly died, and 20 others saw their conditions worsen after treatment, according to Beijing News.

Liu Boqian contributed to this story.