Incidents ranging from Chinese dog treats pulled from U.S. pet stores to the virus that has killed millions of American piglets has raised concerns about the safety of food and feed imports from China, lawmakers said on Friday.

The problems “have highlighted concerns over the effectiveness of China’s food safety regulation, the effectiveness of U.S. government regulation of imported foods from China, and the overall safety of such foods,” said Democratic Senator Sherrod Brown of Ohio and Republican Representative Christopher Smith of New Jersey.

The U.S. Congressional-Executive Commission on China has scheduled a hearing for Tuesday, “Pet Treats and Processed Chicken from China: Concerns for American Consumers and Pets,” to consider those issues.

Two major U.S. pet food chains this week pulled Chinese-made dog and cat treats, such as jerky strips, after they were linked to the death of some 1,000 dogs in the United States and Canada, according to media reports.

The U.S. Food and Drug Administration has been investigating dog illnesses linked to Chinese jerky since 2007. As of May 1 it had received about 4,800 reports of such illnesses.

The commission noted that researchers are exploring a possible link between China and the domestic outbreak of Porcine Epidemic Diarrhea Virus (PEDv), which has killed over 7 million piglets across the United States.

PEDv, which causes diarrhea and vomiting in pigs but is not a threat to human health, likely originated in China’s Anhui province.

The commission also highlighted the practice of shipping U.S. chicken to China for processing and re-export to the United States.

Top witnesses at Tuesday’s hearing will be Daniel Engeljohn from the Department of Agriculture’s Food Safety and Inspection Service, and Tracey Forfa of the FDA’s Center for Veterinary Medicine.

The commission comprises members of Congress and the administration, and was originally created to monitor China’s compliance with international human rights standards.

(Reporting by Ros Krasny; Editing by Eric Beech)