OTTAWA, CANADA

Canada's post office and police are trying to track down a "rogue elf" who wrote obscene letters to children on behalf of Santa Claus.

The Ottawa Citizen said at least 10 nasty letters had been delivered to little girls and boys in Ottawa who wrote to Santa this year care of the North Pole, which has a special H0H 0H0 Canadian postal code. Return letters from Santa are in fact written by an 11,000-strong army of Canada Post employees and volunteers.

"We firmly believe there is just one rogue elf out there," a Canada Post spokeswoman told the paper.

Canada Post's popular "Write to Santa" program -- which last year delivered more than a million letters to children in Canada and around the world -- has been shut down in Ottawa until the offender is caught.