Chemnutra has denied knowledge of the alleged contamination
Two Chinese companies and an American food products importer have been indicted in the US for their alleged role in a tainted pet food scandal.
Prosecutors allege thousands of cats and dogs across the US died last year after traces of toxic chemical melamine were found in 150 brands of pet food.
They claim the contamination was traced to wheat protein imported from China by Las Vegas-based Chemnutra.
Chemnutra said it denied "any intent to defraud or knowledge of wrongdoing".
'Death or injury'
The two Chinese companies indicted are Xuzhou Anying Biologic Technology Development, and Suzhou Textiles, Silk, Light Industrial Products Arts and Crafts.
Bosses at the two firms, and the owners of Chemnutra, have also been charged individually.
Prosecutors say the affected animals died as a result of kidney failure.
"In today's global economy, crimes that occur halfway around the world can seriously impact our lives," said US Attorney John Wood.
Chemnutra said in a statement that prosecutors do not allege that its owners, Sally and Stephen Miller, "knew of the presence of melamine or any other substance that would cause death or injury to animals".
"The Millers unequivocally support the government pursuing those with knowledge of the dangerous contaminants," it added.
"However, they are deeply bothered by the government's failure to make these important distinctions in its press release related to their indictment."
Wider Chinese scares
Melamine is used to create plastics, fertilisers and cleaning products.
It has no approved use as an ingredient in either human or animal food in the US.
The issue is one of a number of health scares to hit Chinese exports last year.
Products, from Chinese-made tinned meat to toothpaste and children's toys, have also had to be removed from shelves in the US and around the world.
While the Chinese government has vowed to improve health and safety standards, only last week at least 10 people in Japan needed medical treatment after they were taken ill after eating Chinese-made dumplings.