Wei Zexi, 21, died last month of a rare form of cancer.
He had turned to Baidu to look online for the best place for treatment, finding a department under the Second Hospital of Beijing Armed Police Corps which offered an experimental form of treatment that ultimately failed, according to state media.
Before dying, Wei had posted criticism online accusing Baidu of promoting false medical information, as well as the hospital for misleading advertising in claiming a high success rate for the experimental treatment, state radio said.
"Wei's family says they trusted the treatment because it was promoted by one of the military hospitals which are considered credible, and the attending doctor had appeared on many mainstream media platforms," state radio said.
The regulator said in a short statement Wei's case had attracted widespread attention on the Internet.
It, along with the health ministry and State Administration for Industry and Commerce, would investigate Baidu over the case and "handle it in accordance with the law" and publicise its findings.
Baidu said in a statement it deeply regretted Wei's death and sent its condolences 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," it said.
The company added it welcomed the investigation and would fully cooperate.
Reuters was not able to reach the hospital for comment.
Baidu has been in trouble before for medical related issues.
This year, it was criticised for selling management rights for an online forum related to haemophilia to an unlicensed private hospital, which then used the platform for self-promotion and deleted comments that challenged its credentials, the official Xinhua news agency said.
In 2010, China's state-run television accused Baidu of promoting counterfeit drugs through its search engine.
© Thomson Reuters 2016
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