In the third known incident since this January, evidence of tampering was discovered in several foods at the Oakridge Co-op store on Thursday morning. (QMI Agency file photo)

CALGARY - For the third time this winter and in more items than ever, metal objects have been found pressed into food at the Oakridge Calgary Co-op store.

Just prior to opening Thursday, staff members spotted clothing pins in packaged flatbread and deli cheese items -- which were plainly visible -- at the Oakridge Centre location.

A subsequent search uncovered more tampering -- this time in a total of eight food items, said Co-op spokeswoman Sarah Boutron.

"Our centre employees are now very good at this. They continue to do this searching every day," she said.

City police say they still don't know what's driving whoever's tampering with the food, said Sgt. Don Coleman.

"Until we scoop somebody, I can't speculate on the motivation," said Coleman, adding the culprit is extremely bold following similar incidents on Jan. 18 and Feb. 17. "For sure, it's had lots of publicity ... it's fairly overt the way the items have been tampered with."

Co-op said it's increased security in the store since the earlier incidents. "The Co-op's been very diligent and are doing the best they can and so are we," said Coleman.

While camera surveillance footage is being reviewed, "I'm not sure if there are any camera captures," said Coleman. After Thursday's discovery, staff was examining other items for possible tampering but the store wasn't closed for any period of time.

The grocery chain is urging the public to check bakery, produce, dairy and other fresh food items for tampering and said it will refund customers for any questionable articles.

Police are seeking the public's help in solving the cases. "We're making some progress but public assistance would be great," said Coleman.

bill.kaufmann@sunmedia.ca