Good Guide has issued a statement on its website regarding the testing of the Go Go Hamsters.
The statement is from Dara O'Rourke (pictured), a professor in the department of environmental science, policy and management at UC Berkeley.
He said: "As we explained in our original press release, we tested the Zhu Zhu pet using a NITON XL3t series X-ray fluorescence (XRF) analyzer.
"XRF technology is a method that measures the "total" contaminants present on the surface of the toy.
"We did not test these toys using the new government standard for toy companies to determine the "soluble" level of contaminants in a toy.
"The federal standard for antimony is 60 parts per million soluble. We found antimony between 93-106 parts per million total on the surface of the toy.
"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."