Waikato police are investigating an incident in which a bolt was fired through a glass ranch slider at an elderly woman's Whangamata home on New Year's Day.
Senior Sergeant Rupert Friend of Whangamata police said the woman was woken at her Weka St home by a loud bang about 1am.
"At first she thought it might have been a rock thrown through her window," he said.
Neighbours immediately came to make sure the woman was alright, he said.
It wasn't until sunrise that the woman saw the half-inch bolt lying on her lounge room floor and she contacted police.
Mr Friend said the bolt smelled of gunpowder, and a search by police of the road revealed cardboard tubing from fireworks that had been unrolled to get at the gunpowder.
"We're appealing for anyone in the vicinity of Weka St, Whangamata around 1am who may have noticed anything suspicious."