China's top quality supervisor said on Tuesday that tests had found no direct evidence to connect pet sickness in the United States to snacks made in China.

The General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ) said tests -- conducted by it and the US Food and Drug Administration -- had not confirmed any connection and had not detected any poisonous or hazardous ingredients in the snacks, despite allegations that they were the cause of widespread illness and death in US pets.

The AQSIQ did not specify what brand or snack variety was under investigation.

The statement came after US pet specialty retailer Petco announced earlier this month that it was pulling all pet treats made in China from its 1,300 stores because of concerns they had caused sickness in thousands of pets and killed more than 1,000 dogs in the US since 2007. Phoenix-based PetSmart Inc. also plans to remove the treats from its stores by March.

China will closely follow events and hopes the parties concerned can remain objective and rational, the AQSIQ said in a statement on its website.

According to statistics from AQSIQ, China exported 98,000 tonnes of pet food in 2014, of which 35,000 tonnes went to the US market.