VANCOUVER, British Columbia (AP) _ Thousands of turkeys were pulled from supermarket shelves after an animal rights group claimed it had injected them with rat poison.

The threat came in an anomymous letter Friday, on what local supermarket executives said would have been the biggest day of the year for turkey sales - 18,000 at one chain alone.

The letter from a group calling itself the Animal Rights Militia was delivered to two of the city's biggest chains - Save-On Foods and Canada Safeway - and to news organizations.

Police Constable Anne Drennan said the group claimed it was acting ''in the name of turkey rights, avenging the senseless slaughter of millions of turkeys.''

In 1992, Canadian Cold Buster candy bars were withdrawn from sale in five provinces after the same group said it had injected 87 bars with liquid oven cleaner to protest the use of laboratory animals to test the energy bar. Police found a corrosive substance in one bar.

Police were checking sources familiar with political and social activists for leads on the turkey threat, Drennan said.

''This is a very, very difficult case to investigate,'' she said. ''We have so very little to go on at this point.''

She called the episode bizarre, adding that the group sent a dead chicken - not a turkey - to a local television station.

Toxicology tests revealed no poison, she said, and forensic tests of the box that had contained the chicken had not yet revealed any clues.

''This is no prank,'' said the letter from the group. ''Ignore this warning and you will be accountable. Nobody eats the turkeys, nobody gets hurt.''

Canada Safeway spokesman Don Bell said the threat covered turkeys sold in the chain's more than 50 stores in the metropolitan area in the last week.

''Anyone who has a turkey at home that was purchased in that period, just take it back to the store and we'll issue a full refund,'' he said. ''We will be having fresh stock hopefully in the stores either tonight or tomorrow.''

Gillian Willis, supervisor of poison information for the British Columbia Drug and Poison Information Centre, said rat poison in turkey is unlikely to cause major injury.

The poison doesn't have any taste, Willis said. Symptoms include bleeding gums, nosebleeds or bruising without apparent reason.

''Probably the amount they ingest from eating two slices of turkey meat is unlikely to cause some serious injury, but certainly if they have eaten any they should call the poison control center and check into the (hospital) emergency department,'' Willis said.