Dog owners are being warned to keep a close eye on their pets after a disturbing discovery at a popular Vancouver park.

Dogs have found and eaten abandoned pieces of pizza stuffed with sewing needles in an off-leash area of Strathcona Park twice in the past few weeks.

In one case, an owner noticed her dog had a piece of food in his mouth, and saw a string hanging out of his mouth as he was about to swallow.

"I pulled it out and it was a bundled up piece of pizza that had been sewn together," DJ Larkin told CTV News.

She threw it out, thinking it was strange but hoping it was an isolated incident, but when she heard another dog was injured in a similar incident, she felt compelled to come forward.

The other dog swallowed the ball of pizza, which had several needles in it, and needed surgery to remove one from its throat.

The incidents have been reported to the City of Vancouver, and officials say they're investigating. Larkin said she's also been in touch with the BC SPCA.

"It's so upsetting because it's a really popular park for East Van dog owners, and I can't imagine any reason to do that except to intentionally injure an animal," she said.

Larkin said she's never had any other experiences with strange things found in the park, but said she'd heard reports of people finding rat poison left out in the area.

The dog owner says she no longer feels comfortable bringing her dog to the park, and others who were at the grounds on Friday said they're keeping a close eye on their animals.

With a report from CTV Vancouver's Ben Miljure