Waterloo Regional Police are advising parents to speak to their children about stranger safety after a disturbing incident at a Kitchener school.

Police say an unknown woman was spotted walking around Our Lady Grace Public School on Gracefield Crescent in Kitchener just after 9am Wednesday.

Police say two teachers approached her and she told them she was lost. She then left.

However, police say she returned just before four that afternoon and approached a 10-year-old girl and told her she was there to pick her up. She did not know her so she went to tell an adult.

Police are still looking for the woman.