Bacteria-contaminated herbal injections caused the deaths of three patients in southwestern China, state media reported Tuesday.

Tests on samples of a ginsing injection used on heart patients showed the product had been "tainted by bacteria," the State Food and Drug Administration and Ministry of Health said in a statement Tuesday, according to the official Xinhua News Agency.

The statement did not identify the type of bacteria and only said the investigation is continuing into how the contamination took place.

The medication is an extract from the herb Ciwujia, a type of Siberian ginseng, which is injected into patients who suffer from thrombosis and heart disease.

Six patients in southwestern Yunnan Province became violently ill after receiving a Ciwujia injection, with symptoms including vomiting or slipping into a coma. Three of the patients died in the hospital on Oct. 6. The others were described as stable but were still under observation.

On Monday, the drug safety agency ordered the drug's producer, Wandashan Pharmaceutical Company in northeastern Heilongjiang Province, to recall all of its Ciwujia injection products.

China's pharmaceutical industry is highly lucrative but poorly regulated, resulting in companies trying to cash in by substituting fake or substandard ingredients. In recent years, a string of fatalities blamed on counterfeit or shoddily made medications have been reported.

The troubles also extend to regulatory bodies. Last year, amid an uproar over the safety of Chinese exports, the country's former top drug regulator was executed for taking millions of dollars in bribes to approve substandard medicines, including an antibiotic that killed at least 10 people.