HONG KONG (AP) _ Hong Kong suspended beef imports Tuesday from a California processing plant run by Harris Ranch Beef Co. after its beef violated precautions against mad cow disease by including bone.

Hong Kong currently only allows the import of U.S. boneless beef from cattle less than 30 months old, with high-risk body parts such as the brain and spinal cord removed.

The policy replaced a two-year total ban on U.S. beef in late December.

Hong Kong has already banned beef imports from two other U.S. meat processing companies for violating the new policy.

A spokesman at Harris Ranch, based in Selma, California, said the bone found Monday at Hong Kong's airport was about a sliver about half an inch (1.3 centimeters) long.

"We're taking the matter seriously," said Bruce Berven, marketing vice president. "But obviously bones are part of a beef carcass. When you're processing meat, you're going to have bone."

Harris Ranch has sent about 9,000 kilograms (20,000 pounds) of beef, less than 1 percent of the company's exports, to Hong Kong since it resumed exporting there in January.

Berven does not know when exports to Hong Kong will resume. The company is one of the leading beef exporters in California, though a midsize player in the U.S. beef industry, he said.

"One always wonders how incidents like this will affect the reopening of markets to other nations," Berven said.

Japan and South Korea, two of the largest foreign markets for U.S. beef, have also shut their doors to the product over concerns about mad cow disease.

Mad cow disease, or bovine spongiform encephalopathy, is a degenerative nerve disease in cattle. In people, eating contaminated meat products is linked to a rare but fatal disease called variant Creutzfeldt Jakob disease.