Japan suspended beef imports from a Nebraska processing plant after finding meat in a shipment that may violate a regulation imposed over mad cow concerns, the Associated Press reports. Plant owner Tyson Foods Inc. acknowledged the problem, saying the boxes of beef were mistakenly included in a shipment destined for export from its Tyson Fresh Meats plant in Lexington, Neb. He said Tyson would continue to serve its Japanese beef customers through its six other U.S. beef processing plants and will take further steps to ensure only qualified product is being exported to Japan. The Ministries of Health and Agriculture said inspectors at the port of Yokohama found the two boxes of meat, which were not recorded in the accompanying shipping documents. The shipment''s importer could not confirm that the meat met the government requirement that all beef destined for Japan be from animals age 20 months or younger, the ministries said in a statement. Younger animals are believed less likely to be infected with mad cow disease, the common name for bovine spongiform encephalopathy. U.S. officials have told Japan the boxes were erroneously included in the shipment, the statement said. No banned materials have been found in the shipment, which consisted of about nine tons of frozen beef, the statement said.