The F.D.A. sent a warning letter on Monday to Changzhou SPL, the Chinese plant identified as the source of contaminated heparin made by Baxter International in the United States. It warned that the plant used unclean tanks to make heparin, that it accepted raw materials from an unacceptable vendor and that it had no adequate way to remove impurities.

Heparin is made from the mucous membranes of the intestines of slaughtered pigs that, in China, are often cooked in unregulated family workshops. The contaminant, identified as oversulfated chondroitin sulfate, a cheaper substance, slipped through the usual testing and was recognized only after more sophisticated tests were used.

The F.D.A. has identified 12 Chinese companies that have supplied contaminated heparin to 11 countries  Australia, Canada, China, Denmark, France, Germany, Italy, Japan, the Netherlands, New Zealand and the United States. Deborah Autor, director of compliance at the F.D.A.’s drug center, said the agency did not know the original source of all the contamination or the points in the supply chain at which it was added.

Officials have discovered heparin lots that included the cheap fake additive manufactured as early as early as 2006, although a spike in illnesses associated with contaminated heparin began in November and persisted through February, officials said.

Separately, the Government Accountability Office will release a report on Tuesday showing that the F.D.A. would need to spend at least $56 million more next year to begin full inspections of foreign plants. It would need to spend at least $15 million annually to inspect China’s drug plants every two years, which is the domestic standard.

Bush administration officials have acknowledged problems associated with poor inspection of overseas plants and have plans to improve the situation. But President Bush’s budget does not provide the F.D.A. with funds to hire more inspectors.

At its present inspection pace, the F.D.A. would need at least 27 years to inspect every foreign medical device plant that exports to the United States, 13 years to check every foreign drug plant and 1,900 years to examine every foreign food plant.