BEIJING -- China's national drug watchdog said on Thursday that all suspect "Xinfu" antibiotic injections, which have allegedly caused six deaths in the country, must be recalled by August 31.

The State Food and Drug Administration (SFDA) instructed the drug's manufacturer, Anhui Huayuan Worldbest Biology Pharmacy Co., to retrieve all the "Xinfu" drug it produced in June and July before the deadline.

The administration demanded that all provincial drug departments strengthen supervision of recall work within their jurisdictions, and tighten checks on hospitals, clinics and drugstores.

The administration has discovered that the problematic injection, produced by Huayuan company in June and July, was not properly sterilized, with both sterilization temperature and time being below the state-required safety level.

Since the first reports about problems with the injection came in on July 27, the drug has been blamed for killing six and making at least 80 people sick. Severe adverse reactions include chest, kidney or stomach pains, vomiting and anaphylactic shock.

The "Xinfu" drug produced before June could still be in use, said the administration, but local departments should be vigilant about cases of adverse reactions in patients who take the drug.

Earlier investigation results showed the company had produced 3.7 million bottles of drug since June, with more than 3.18 million bottles sold in 26 provinces across China.

So far, more than 1.2 million bottles of the drug have been recalled, 173,007 are en route back to the factory, and 403,170 bottles have been located and sealed up in other areas.

The remaining quantities, estimated at more than 1 million bottles, might have been used or are scattered in hospitals, clinics and drugstores in small cities and remote rural areas, making them difficult to retrieve, according to the administration.

The administration said that it would "comb every corner" and trace every single bottle of the "Xinfu" drug.

The drug, which used to be a prescription medicine, has been banned by the Ministry of Health following the reports, so the situation is basically under control, the administration said.