Officials in Shanghai are investigating reports that a Chinese pharmaceutical company may have sold more than 12,000 units of a blood plasma product contaminated with H.I.V., potentially the latest in a series of scandals that have threatened to undermine public trust in China’s medical institutions and health care system.

In a statement on its website, the Shanghai Food and Drug Administration said Wednesday night that authorities had ordered the company, Shanghai Xinxing Medicine Company, to begin an emergency recall of the potentially tainted batch of intravenous immunoglobulin, a treatment made from pooled blood plasma that is often used to treat immune disorders, and halt its production.

China’s National Health Commission and the State Drug Administration have asked all medical institutions across the country to stop using the units in question and monitor patients who have already been administered the treatment, according to state news media. Officials did not say how many patients had been treated with the blood product.

“In the spirit of being highly responsible to the people, the local authorities are responsible for conducting follow-up observations of relevant patients and cooperating with the State Drug Administration,” said a report published Wednesday by Xinhua, China’s official news agency.

The presence of H.I.V. antibodies in the treatment was first detected by the Jiangxi Provincial Center for Disease Control and Prevention, in southeast China. A representative of the province’s health commission told The Beijing News on Wednesday morning that, so far, no patients had been found to have been infected with H.I.V. as a result of the treatment.

Founded in 2000, Shanghai Xinxing is a subsidiary of China Meheco Group Co., Ltd., a pharmaceutical company based in Beijing whose controlling shareholder is China General Technology Group, a state-owned enterprise directly administered by the central government.

Just last month, China’s State Drug Administration revised the health warnings on human immunoglobulin products to note that although plasma treatments are screened for pathogens, they nonetheless derive from human blood and therefore may still pose a minor risk of infection to patients.

The investigation into Shanghai Xinxing comes at a delicate time for the ruling Communist Party, which is already seeking to minimize the destabilizing effects of a nationwide economic slowdown. It also represents a setback to President Xi Jinping’s efforts to restore confidence in China’s pharmaceutical industry at a time when the country is pushing to play a bigger role in the global drug industry.

Last month, hundreds of angry parents protested against local government officials in a town in eastern China when it was revealed that more than 100 children had received expired polio vaccines. Months earlier, hundreds of thousands of children across China were reportedly injected with faulty vaccines for diphtheria, tetanus and whooping cough. After protests by parents, the government imposed a record fine of $1.3 billion on the vaccine maker, Changchun Changsheng Biotechnology Company.

But despite years of similar food and medicine scandals, relatively few people have been charged with crimes, fueling frustrations among the public and criticism that the government has not done enough to clean up the industry and enforce regulations.

Late on Wednesday night, the National Medical Products Administration released a statement declaring that although the investigation was still ongoing, preliminary results showed that the blood products in question had tested negative for H.I.V. and the hepatitis B and hepatitis C viruses.

Though the reports about the potentially tainted treatment emerged during the annual Lunar New Year celebrations, when large swaths of the country typically grind to a halt, the news did not go unnoticed.

“The cleanup is always fast, pretty soon they’ll say injecting this product is good for your health,” Cui Yongyuan, a Chinese television host and producer, wrote on the microblogging site Sina Weibo, commenting on a report about the investigation’s preliminary results.

“Tainted milk powder, no problem. Tainted vaccines, no problem. Tainted inoculations, no problem,” he added. “In short, if a few people die, no problem.”