Meatballs found laced with rat poison which were found in in the area of Crestline, Burnett and Parkridge Drives in San Francisco. (San Francisco Police)

SAN FRANCISCO (CBS SF) – Pet owners were advised to be on alert after poisonous meatballs, similar to hundreds found last July, were found Saturday in San Francisco’s Twin Peaks neighborhood, according to a San Francisco Animal Control spokeswoman.

Twenty-one poisonous meatballs that may have been intended to harm or kill pets were found hidden in bushes and shrubs in the vicinity of Crestline and Parkridge drives in the city’s Twin Peaks neighborhood Saturday morning, Animal Care & Control Volunteer Coordinator Deb Campbell said.

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, Campbell said.

Pet owners are being advised to keep cats indoors and dogs on a short leash until the situation is resolved.

The San Francisco Police Department is also asking the public for assistance. Anyone with information regarding the investigation are encouraged to call the SFPD anonymous tip line at (415) 575-4444.

In July 2013, hundreds of tainted meatballs were found in San Francisco’s Twin peaks and Diamond Heights neighborhoods containing levels of strychnine potentially lethal to humans, according to police.

The meatballs were believed to have been left to kill dogs, and one dog that ate the meatballs in July, a dachshund named Oskar, died as a result, Campbell said.

In July, police advised residents who encountered the meatballs to call 911 and only to handle them if absolutely necessary and with heavy gloves as the poison can be absorbed through the skin.

The meatballs found in July had apparently been deliberately placed in spots where dogs defecate in the area of Crestline, Burnett and Parkridge drives, according to police.

Campbell said that if an animal is believed to have eaten the meatballs the animal should be taken to a veterinarian immediately. San Francisco Veterinary Services, Pets Unlimited and All Pets offer 24-hour vet service, she said.

Additionally, a reward announced in July for information about suspects who left out the poisoned meatballs reached $5,000, according to a spokeswoman for the Animal Legal Defense Fund said.

The animal defense organization teamed with VegNews Magazine and Yelp CEO Jeremy Stoppelman to offer the reward in July for any information leading to the arrest and conviction of perpetrators in the crime.

“The citizens of San Francisco are up in arms over this sadistic crime,” Animal Legal Defense Fund Executive Director Stephen Wells said in a statement last summer.

Police have not identified the person responsible for placing the poisonous meatballs in the neighborhood and have not determined which poison is in this batch of meatballs found Saturday.