Regulators in China are investigating Baidu over the death of a student who used the search engine to look up cancer treatments.
Wei Zexi, aged 21, a computer science student at Xidian University, died last month of a rare form of cancer.
Shares slumped in the US on news of an investigation, with Baidu’s Nasdaq-listed shares falling 7.92%.
Baidu has said on its Weibo account that it had filed a request for the hospital to be investigated.
According to state media, Wei was diagnosed with synovial sarcoma in 2014. He had been undergoing a controversial treatment at a hospital which was advertised on the search engine.
The company, often referred to as China’s Google, told the BBC: “We deeply regret the death of Wei Zexi and our condolences go out to his family.
“Baidu strives to provide a safe and trustworthy search experience for our users, and have launched an immediate investigation of the matter.”
China’s internet regulator – Cyberspace Administration of China – is teaming up with several other government agencies to look into the matter, including the State Administration of Industry and Commerce, and the National Health and Family Planning Commission.