Calgary police have scaled back reporting details of the latest two cases of food tampering at city grocery stores in an effort to discourage copycats.

Small metal items were embedded in a bakery item and an apple at two unnamed southeast grocery stores between Friday and Monday, police said.

There have been 13 incidents of metal items, including push pins, discovered in grocery items at various chains across Calgary since January.

"We believe firmly that many of these are copycat incidents, and that the constant media attention given to each event is only fuelling this behaviour," police said in a statement on Monday.

Last week, Calgary's police chief said the force would no longer be holding news conferences to highlight the disturbing cases, but acknowledged it also had to somehow balance the public's right to know.

Shoppers are still encouraged to check their groceries carefully for foreign objects when they get home, said police.

The Canadian Council of Grocery Distributors, which represents major grocery chains including those targeted, is offering a $10,000 reward for an arrest and conviction.