A consumer group contends one of the holiday season's must-have toys is unsafe.

But the maker of the robotic Zhu Zhu Pets hamsters defended its product Saturday against a study by San Francisco-based GoodGuide that said higher-than-allowed levels of the chemical antimony were found in the toy.

Good Guide named Zhu Zhu Pets hamsters one of the top-selling toys with low ratings after finding antimony, which can cause health problems, on the hair and nose of one of the toy hamsters, called Mr. Squiggles.

The group assigned the toy, aimed at 3- to 10-year-olds, a rating of 5.2 on a 10-point scale.

But the toy's maker, St. Louis-based Cepia LLC, insisted in a statement that its product is safe and has passed rigorous testing. The company said it was contacting GoodGuide to share its testing data and determine how the report was founded.

"I have been in the toy industry for more than 35 years, and being a father of children myself, I would never allow any substandard or unsafe product to hit the shelves," Russ Hornsby, Cepia's CEO, said in the statement.

Zhu Zhu Pets, which retail for about $10, have become this season's toy craze, following in the footsteps of Tickle Me Elmo and Cabbage Patch Kids. The items fetch $40 or more on resale Web sites like eBay and Craigslist.

That's what brought it to GoodGuide's attention. GoodGuide CEO Dara O'Rourke told The Associated Press on Saturday that his group bought three of each of the year's 30 hottest toys and tested them multiple times.

Antimony was measured at 93 parts per million in the hamster's fur and at 106 parts per million in its nose. Both readings exceed the allowable level of 60 parts per million, said O'Rourke, an associate professor of environmental science at the University of California, Berkeley.

O'Rourke said GoodGuide's test results, released Friday, also indicated the possibility that some toys contained phthalates, chemicals that were subject to tougher standards in the Consumer Protection Safety Improvement Act passed last year.