TOKYO : Japan's farm ministry said Friday that it had found ground beef in a shipment from the United States that violates a ban imposed due to concerns over mad cow disease.

A Japanese importer on Thursday found 298 boxes containing 3.8 tonnes of US beef without sanitary certification, a requirement under a trade accord between the two countries, a farm ministry official said.

The ministry immediately slapped a ban on imports of beef from the meat packer involved, which is located in Kansas, the official said.

"Then we found 4.5 kilograms (10 pounds) of ground meat in one of the boxes," the official said. "We will continue the ban indefinitely until safety is confirmed."

Japan currently allows imports of US beef from cattle aged 20 months or younger, which Washington protests, noting that the World Organisation for Animal Health (OIE) has already declared US beef safe.

Processed meat such as ground beef and sausages are among banned items.

Japan banned US beef in December 2003 after the brain-wasting cattle disease, bovine spongiform encephalopathy (BSE), was found in a US herd. Japan had until then been the US cattle industry's biggest export market.

The ban nearly grew into a full-blown trade war, with US farm-state senators pressing for sanctions unless Tokyo opened up its markets by the end of 2005.

Japan agreed in 2006 to resume US beef imports on condition age limits be imposed on cattle at the time of slaughter, believing younger cows are less likely to have accumulated infectious proteins that could cause the disease.

- AFP /ls