Police in Delta, B.C., south of Vancouver, are warning parents to check their children's Halloween candy carefully after a 21-year-old woman bit into a chocolate bar and found a razor blade.

The woman was escorting a group of neighbourhood children around the Imperial Village area of Tsawwassen Sunday night and the tampered chocolate bar came from one of the children's bags. She ate the candy on Monday, and was surprised to bite down into a razor blade.

Police say the victim wasn't sure whether the blade had been inserted through the candy wrapper or if the wrapper had been partially opened and the blade stuck directly into the chocolate. She was unhurt.

This isn't the first time area police have sounded the alarm over tampered candy on Halloween.

Vancouver police issued a warning in 2006 after Tylenol 500 painkillers were found amongst candy grab bags given out to kids in South Vancouver. No illnesses were reported.

The year before, Mission RCMP reported a boy had found a three-inch X-Acto knife in a piece of candy. And Vernon RCMP say a little girl found a sewing needle stuck into her Reese's Peanut Butter Cup.

Delta police say this latest incident is a reminder that everyone should be cautious when consuming their Halloween goodies.

"Sadly there are sick minded people who derive some sort of twisted pleasure from endangering the innocent, and in this incident the likely targets are children," Const. Sharlene Brooks said in a statement.