Farm minister Tsutomu Takebe pledged Tuesday to maintain a ban on the distribution of 13,000 tons of beef from cows butchered before nationwide cattle testing began for mad cow disease on Oct. 18.

The Agriculture, Forestry and Fisheries Ministry "will never authorize distribution of this beef," Takebe told a news conference.

By ministry order, beef producers and wholesalers have stored 13,000 tons of beef in refrigerated warehouses made from cows slaughtered before the examinations began.

As for what to do with the beef, Takebe said, "There are a range of options, including incineration."

When a cow is butchered for human consumption, its brain and spinal cord are removed. But under the testing regimen introduced Oct. 18, examiners need to analyze the brain tissue of cows destined for slaughter, which number about 1.3 million annually in Japan.

Takebe also promised to look into a news report that a ministry official in 1991 pressured a Nihon University researcher who warned farmers about importing cattle suspected of having the disease from U.S. cattle breeders near Chicago. The official reportedly told the researcher not to repeat the warning.

"Although the incident concerns an event from 10 years ago, the ministry takes it seriously and will check the truthfulness of the allegations," Takebe said.

The Nihon Keizai Shimbun reported Tuesday that the researcher told a meeting of farmers in 1991 that it is dangerous to import cattle from the Chicago area, where outbreaks of scrapie disease in sheep -- whose carcasses are made into meat and bone meal for cows -- had been reported.

Scrapie is a fatal, infectious disease that affects the central nervous system of sheep. It is similar to mad cow disease.

Takebe said he will have the ministry provide information about the reported incident to a new advisory council on the disease that reports to farm and health ministers. The council of academics met for the first time Monday, when the reported meddling by the ministry official was disclosed.

Mad cow disease is believed to arise from cows being fed infected meat and bone meal. Human consumption of infected beef is thought to cause a new variant of the fatal Creutzfeldt-Jakob disease.