Pet owners were advised to be on alert Saturday after poisonous meatballs - similar to hundreds found last July - were found that morning in San Francisco's Twin Peaks neighborhood.

Twenty-one poisonous meatballs that may have been intended to harm or kill pets were found hidden in bushes and shrubs. Animal control officers have posted signs in the area alerting pet owners to the hazard and are encouraging people to be on the lookout for additional poisoned meatballs. Pet owners are being advised to keep cats indoors and dogs on a short leash until the situation is resolved.