Products billed as "microwave safe" can release toxic doses of the chemical bisphenol A when heated, according to a lab analysis. The amounts detected were at levels that scientists have found cause neurological and developmental damage in laboratory animals.

The test results raise new questions about the chemical and the safety of an entire inventory of plastic products labeled as "microwave safe." BPA is a key ingredient in common household plastics. It has been found in 93 percent of Americans tested.

Although BPA is commonly thought to be found only in hard, clear plastic and in the lining of metal food cans. In fact, it is present in such products as frozen food trays, microwaveable soup containers and plastic baby food packaging.

Food companies advise parents worried about BPA to avoid microwaving food in plastic containers, especially those with the recycling number 7 stamped on the bottom. But tests also found BPA leaching from containers with different recycling numbers, including numbers 1, 2 and 5.

"There is no such thing as safe microwaveable plastic," said Frederick vom Saal, a University of Missouri researcher who oversaw the newspaper's testing.