BEIJING, Nov. 22 (Xinhuanet) -- Less than four months after it eased a ban on U.S. beef, Japan on Wednesday halted beef imports from an American meatpacking plant after finding a shipment with improper documentation.

    Japan's Agriculture and Health ministries decided to stop shipments from Swift and Company's plant in Greeley, Colo. after a shipment from the facility arrived in Osaka without proper documentation for some of the internal organs contained within, Agriculture Ministry official Yasushi Yamaguchi said.

    "We are very concerned about what appears to be a simple error because it comes so soon after Japan lifted its import ban," Yamaguchi said. The suspect package was only one of 760 boxes containing 11 tons of frozen beef and beef tongue.

    The Japanese government has requested that the U.S. government investigate the mishap and present a plan to prevent a recurrence, Yamaguchi said. The Japanese will send a delegation to the Greeley plant after receiving the report to review whether it is following rules for export to Japan before allowing trade to continue.

    Only a select list of U.S. meat exporters are allowed to ship to Japan and the cows must be 20 months old or younger. Many Japanese remain worried about mad cow disease, a degenerative nerve disease found in older cattle that has been linked to the rare but fatal human variant Creutzfeldt-Jakob disease, and are unsure of U.S. safeguard measures.

    The internal organs in the suspect shipment were not deemed at-risk meat parts for mad cow disease, but they triggered alarm because they were shipped without the proper customs documentation, Yamaguchi said.

    Tokyo eased its two-year blanket ban on U.S. beef in July, ending a long-standing trade dispute that pit U.S. ranchers against Japanese health officials who were worried about the risk of mad cow disease.

    Japan first banned American beef in December 2003 after the first reported case of mad cow disease in a U.S. herd.

    It eased the ban in July after U.S. and Japanese officials hammered out a deal that included strict restrictions and stringent checks at U.S. meat processing plants.

    The other boxes in the shipment had the proper paperwork.

    (Agencies)