SHANGHAI, China - China's food and drug officials are investigating a company suspected of using illegally procured blood stocks to make immunoglobulin and other drugs, infecting patients with hepatitis C.

Guangdong Bioyee Pharmaceutical "acted illegally in the production of immunoglobulin and some products had caused hepatitis C infections in patients," the State Food and Drug Administration said in a statement posted on its website.

The case is the latest in a series of reports of substandard, bogus or tainted pharmaceuticals that have prompted calls for stricter enforcement of safety standards.

The national food and drug agency noted that the issue had drawn the attention of top leaders, coming just months after an antibiotics maker was blamed for six deaths and dozens of illnesses after failing to properly sterilize the drug, allowing the growth of dangerous levels of bacteria.

Officials in Guangdong, which borders Hong Kong, refused comment when contacted by phone Wednesday, referring reporters to food and drug agency statements.

Staff at Bioyee's headquarters in the city of Shaoguan also refused comment.

China outlawed blood sales in 2003, after it was discovered that unclean blood buying businesses, especially in the central province of Henan, had passed the HIV/AIDS virus to thousands of people in the 1990s. But with voluntary donations running below demand, reports of the practice persist.

According to media reports, Bioyee is suspected of having made the immunoglobin using illegally acquired, tainted blood and to have allegedly forged its production licences and distributed defective products.

The State Food and Drug Administration ordered the company to suspend production. Pharmacies and medical facilities were warned not to use the product under investigation, which is being confiscated.

A team of investigators was sent to Guangdong to look into the case.

According to Bioyee's website, the company has been operating for more than 30 years, basing its products on pure mountain spring water and first class production conditions.

A statement by the provincial Guangdong Food and Drug Administration seemed to play down the risks from the product, saying that samples taken so far were not found to be tainted. It said experts believed they would not cause users to be infected with hepatitis C - a common blood-borne infection that can cause severe liver damage.

But it urged members of the public to report any problems.

Hong Kong's South China Morning Post newspaper reported Wednesday that a 24-year-old public health student from the southern island of Hainan planned to file suit, saying authorities failed to respond to her complaints that she was infected with hepatitis C after receiving an immunoglobulin injection - meant to boost her immune system - at a Beijing hospital.

"The agencies were sloppy in the administration of quality control and production licenses, and the neglect is ridiculous and unbearable," it quoted the woman, Lu Ting, as saying. "How could they be so unfeeling as to let an illegal producer make defective products and inject them into patients? It's like injecting a virus directly into human bodies."

The newspaper cited unidentified Guangdong officials accusing the provincial health department of a coverup.