BEIJING, May 23 (Reuters) - China's drug watchdog said quality supervisors would be dispatched to all of the country's blood manufacturers to ensure products were free of diseases like HIV and hepatitis, Xinhua news agency reported on Wednesday.

The move comes amid nationwide concern about the safety of China's blood products after a string of health scares in recent months involving tainted blood-based drugs.

"Provincial drug authorities have assigned 84 such supervisors to 33 blood products manufacturers and 32 vaccine makers so far," Xinhua said, quoting an unnamed official at the State Food and Drug Administration, as saying.

Plasma procured would need to be stored for 90 days and screened for viruses such as HIV or Hepatitis C before being used in blood products, Xinhua said.

Blood transfusion is still a major channel for HIV-AIDS transmission in China, and patient infections from blood-based drugs made with tainted plasma are reported sporadically by local media.

In January, the government suspended the production and sale of a blood-based drug used to treat immune system deficiencies after users were feared to have contracted hepatitis C from contaminated plasma.

Hundreds of thousands of farmers in the central province of Henan were infected in the 1990s through schemes in which people sold blood to unsanitary, often state-run health clinics, making the province the centre of China's AIDS epidemic.

Authorities have moved to clean up the country's blood collecting centres in recent years, but underground blood selling has persisted.

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