(CNN) -- A consumer Web site on Monday clarified its previous announcement that one of the hottest-selling toys of the holiday season contains high levels of a potentially hazardous substance, saying its testing method was different from that of the federal government.
The manufacturer of Zhu Zhu Pets, which makes the light-brown hamster called Mister Squiggles, then issued a statement saying the method the group used to identify levels of antimony is "inferior" and has not been determined to be reliable.
In the message on the Web site of California-based GoodGuide, the group's co-founder, Dara O'Rourke said: "While GoodGuide considers the presence of any antimony on the surface of a toy to be a concern, we want to clarify that we used a testing methodology to evaluate the toys that is different from the testing methodology incorporated into the federal standards."
Russ Hornsby, CEO of the toy manufacturer, St. Louis, Missouri-based Cepia LLC, said he was pleased at the clarification.
The testing was conducted using an "inferior testing methodology ... that has 'not been determined to be a reliable test method' by the Consumer Product Safety Commission in August of 2009," Hornsby said in a statement.
However, that determination was made by the commission regarding testing for lead, according to documents on its Web site. The documents said further research was needed before a final determination could be made on the methodology.
"As we have continually stressed, all Zhu Zhu Pets toys are safe and compliant with all U.S. and European standards for consumer health and safety in toys," Hornsby said. Products are tested internally and reviewed by an independent third party, he said.
GoodGuide, according to its Web site, "strives to provide the world's largest and most reliable source of information on the health, environmental and social impacts of products and companies."
O'Rourke told CNN last week that testing found levels of 93 to 106 parts per million of antimony on Mister Squiggles. The new federal standard is about 60 parts per million, she said.
Antimony is used in textiles and plastics to prevent them from catching fire, according to the U.S. Department of Health and Human Services' Agency for Toxic Substance and Disease Registry. Prolonged exposure can cause lung and heart problems, ulcers and diarrhea, according to the U.S. Centers for Disease Control and Prevention.
Bruce Katz, Cepia senior vice president, told CNN the toys "do not contain high levels of antimony in any way."
The toys are popular in Europe as well as in the United States. Their British distributor, Character Options, said the products, sold there as "Go Go Pets," are "fully compliant" with U.S. and European Union standards.
"In addition, as part of Character Options' standard due diligence, the toy has been further tested on three separate occasions by the company's own safety experts and found to fully comply with all EU standards," the company said in a statement issued Sunday.
CNN's Martha Dalton and Brendan Gage contributed to this report.