SAN FRANCISCO -- Police are warning dog owners in the Twin Peaks and Diamond Heights neighborhoods to be on the lookout for poisonous meatballs.

According to the San Francisco Police Department, around 8:30 a.m. a dog on a walk with its owner found and ate a discarded, cooked meatball in the area of Crestline and Burnett streets.

When the owner and the dog returned home, the dog became severely sick and had to be rushed to a veterinarian. Police did not disclose the dog's condition Wednesday night.

The dog's owners and some neighbors went back to the area where the dog picked up the meatball, and found others in the street.

They collected as many as they could find. Police said the meatballs appeared to have been poisoned, but investigators will have to run tests to determine what substance was used.

Authorities say anyone else who finds meatballs in the area should use gloves to handle them and call police.

Anyone with information is asked to contact police or the anonymous tip line at 415-575-4444 or text a tip to TIP411 with SFPD in the beginning of the message.

Contact Katie Nelson at 925-945-4782 or follow her at Twitter.com/katienelson210.