The Food Safety Commission found that tests for the fatal bovine illness on cattle aged 20 months or younger were unable to detect the proteins linked to the fatal bovine illness. Scientists believe the proteins associated with mad cow disease do not accumulate in cows that young.
"We have concluded that the risk of excluding cows younger than 21 months old from inspections is negligible or extremely small," Yasuhiro Yoshikawa, chairman of the panel's scientific experts, told reporters.
Still, scientists don't know enough about the disease to rule out risk completely, the panel said in a statement, which urged Tokyo to improve testing methods.
Japan banned U.S. beef imports in December 2003 after the discovery of the United States' first case of mad cow disease. Washington has been steadily pushing Tokyo to drop the ban, but Japanese officials have insisted that all imported beef come from animals tested for mad cow disease, also called bovine spongiform encephalopathy.