The daily Helsingin Sanomat reports that the vets replaced faulty and substandard samples with others.
According to witnesses, samples were tampered with on a weekly basis. One of the vets has admitted to having switched two samples.
One vet informed authorities about the practice and was subsequently fired.
The switching occurred among samples taken at the Snellman abattoir in Pietarsaari and sent to the National Veterinary and Food Research Institute (EELA).
Some 130,000 BSE samples are taken annually in Finland. One case of BSE or mad cow disease was found in Finland in early December 2001.