Police say an 11-year-old girl in southwestern Ontario has undergone surgery and remains in hospital after eating a piece of Halloween candy that contained a metal object.

Waterloo regional police say the girl, from the Cambridge, Ont.-area, ate a Reese's Peanut Butter Cup that contained the metal piece, the source of which remains under investigation.

They say the girl was first taken to a local hospital and later moved to a Hamilton hospital for surgery.

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Police spokeswoman Cherri Greeno said Friday the girl's condition is not considered life-threatening.

There have been other reports of tainted candy in Ontario this Halloween.

In London, Ont., police say they've been unable to determine exactly where a child received a small chocolate bar containing a needle on Halloween night. They say the child was not injured in that incident.

Police say needles were also found in children's candy in Windsor, Ont., and Chatham, Ont.

Barrie, Ont., police say an 11-year-old boy received a Tootsie Roll containing a pill. They say the pill has been identified as melatonin, a supplement to counter the effects of jet lag, or help people sleep if they have an unusual work schedule or suffer from a circadian rhythm disorder.

Meanwhile, police in New Brunswick are investigating incidents in Fredericton and Bathurst in which a nail and a needle were found in Halloween candy.