China’s biggest search engine Baidu Inc. reported a second straight drop in quarterly revenue on Thursday amid new rules on advertising following the death of a 21-year-old student last year.

Baidu’s revenue fell to 18.21 billion yuan (2.65 billion US dollars) in the fourth quarter of 2016, down 2.6 percent compared to a year earlier.

This was slightly lower than analysts’ expected revenue of 18.23 billion yuan, according to Thomson Reuters I/B/E/S Estimates, but it was within the 17.84-18.38 billion yuan range the company had previously forecast.

Baidu faced a backlash last year over its placement of sponsored health care providers in search results, after a 21-year-old student, Wei Zexi, underwent an experimental cancer treatment he had found using the company’s search engine and died.

Critics said the search engine should do better checks on advertisers who pay for high rankings in online searches.

Officials from the Cyberspace Administration of China, National Health and Family Planning Commission and the State Administration for Industry and Commerce investigated the firm and called on Baidu to rectify the listing of advertisements on its platform, as well as introduce a guarantee mechanism for users’ rights and interests.

Analysts estimate that healthcare accounts for about 20 to 30 percent of Baidu's search revenue, which represents more than 80 percent of the company's total sales.

"During the fourth quarter we largely completed our initiative to ensure that new and existing customers meet our stringent quality requirements," said Baidu’s CFO Jennifer Li said in a statement. "We believe that the impact of these initiatives is mostly behind us and we look forward to 2017 as a time of recovery and growth.”

The company added it wanted “to lead the AI (Artificial Intelligence) wave in China” and would keep up “investment in key AI-enabled initiatives such as financial services, cloud and autonomous driving,” Li added.

Baidu’s net income fell 83.3 percent to 4.13 billion yuan in the last quarter, while its marketing revenue fell 8.2 percent to 16.17 billion yuan.

(With inputs from Reuters)