Americans should avoid two Chinese diet pills because they may contain a drug banned for causing dangerous side effects, the Food and Drug Administration warned Tuesday.

The Chinese products are among several linked to hundreds of illnesses and several deaths in Asian countries this summer, but FDA officials said they had information on only the two in the United States. If others come to their attention the warning will be extended, said spokesman Brad Stone.

The pills are called Chasu Jianfei Diet Capsules and Chasu Gempi, and typically are sold in small markets as alternatives to Western medicine, the FDA said.

The pills apparently contain fenfluramine, a once-popular prescription diet medicine banned in the United States in 1997 after it was linked to a dangerous heart problem.

China's health ministry has banned about a dozen different diet products this summer because they illegally contained fenfluramine. Some of the products have been linked to 560 cases of liver or thyroid illnesses in Japan, and at least eight deaths in Japan, China and Singapore.

Products such as traditional Chinese pills can be sold in this country without approval of the FDA, which usually determines if drugs are safe or work as advertised. But the FDA can crack down if such normally unregulated products are found to be unsafe, so it ordered its agents to watch for any new imports of the Chasu products.

The FDA urged consumers not to take any of the pills already sold, and to notify the agency if they see the products for sale. The FDA may be reached at (888) INFO-FDA.