As European authorities seek to get to the bottom of horse meat scandal, diners there now have even more reason to beware.

Three horse carcasses have tested positive for an equine drug called bute, or phenylbutazone. British food safety officials says that meat may have entered the food chain in France.

Bute is a painkiller and anti-inflammatory used on horses -- but it's considered harmful to humans if ingested.

Authorities across Europe are now testing food for the drug.

A brand of lasagna in Britain tested negative for bute but was found to contain more than 60 percent horse meat.