Two tested cows in northern Japan have shown a positive result indicating a mad-cow disease in preliminary exams late Monday, prefectural official Yoshiyuki Konno said.

On Tuesday, samples were sent to a laboratory to carry out a sound research with regard to the potential danger of a fatal, brain-wasting disease called Creutzfeldt-Jakob disease. The disease had been already seen in the country during the 18-19th centuty.

Final results from the secondary tests conducted by a state-run research center north of Tokyo will be released in several days, he said.

In February, Japan informed about the first noticed human case of mad-cow disease that followed the fatal case of a man with similar symptoms.

Japan took all posssible measures to prevent the exposure of the disease. Japan banned U.S. beef imports after the first case of mad cow was confirmed in Washington state last December. Authorities have checked every cow before its entering the food supply since 2001.

That year, the mad-cow disease, with a formal abbreviaton BSE, was discovered for the first time.