WARSAW, Poland (AP) — One of Poland’s top veterinarians said Thursday that traces of horse-meat DNA have been found in beef samples taken from three meat processors — the first acknowledgement that the country could be a source of the horse meat that fraudulently ended up in processed meat products sold as beef across Europe.

Deputy National Veterinarian Janusz Zwiazek said that the DNA was found in three samples out of 121 tested. They came from cold storage at processing plants in central Poland. The meat arrived there from various suppliers in Poland and abroad, including from the Netherlands, Zwiazek told The Associated Press.

Some 80 more samples are to be tested, and separate tests are needed to determine the proportion of horse meat.

All three contamination cases have been reported to the prosecutors, Zwiazek said.

“I want to find the culprit, or culprits,” he said.

Horse meat has recently been found mixed into beef dishes sold across Europe, including in frozen supermarket meals. It has also been found in meals served at restaurants, schools and hospitals. Authorities say it is a case of fraudulent labeling but does not pose a health risk.

The scandal has drawn attention to the complex and murky trade in meat before it reaches the consumer.