As armed police fired tear gas and stun grenades into a Hamilton home where they thought a violent sex offender was hiding, a neighbour worried about the hole officers had left in her fence.

Semi-retired Margaret Parry was finishing a cup of tea yesterday morning when members of the Hamilton armed offenders squad ran down her driveway.

She said one busted holes in her trellis fence to take aim at her neighbour's house.

"I thought, well I hope you will come back and fix that," said Ms Parry, 73.

Police believed Colin Rangi Robyn Kiriona, who had subjected a 31-year-old woman he knew to a series of violent sexual assaults and held her against her will for 48 hours, was in the Sunnyside Cres house.

But after a tense standoff lasting close to an hour, a growing crowd of onlookers from nearby streets and several rounds of tear gas and stun grenades fired into the house, Ms Parry began to wonder if anyone was actually home.

"There were police all over the place with dogs, guns and tear gas and I kept hearing someone on a loudhailer going, 'residents of ... Sunnyside Cres, come out with your hands up'. I started to think they mustn't be home and sure enough about 90 minutes later a police officer came up and said 'ah, sorry there was no one there'."

Hamilton city area commander Rob Lindsay this morning said police received a number of reports of possible sightings of Kiriona overnight.

"We ask that these continue," he said. "We're following up all possible avenues of inquiry locally while not closing our minds to the possibility he may have fled outside the Waikato."

Yesterday Mr Lindsay said police heard of the 31-year-old woman's plight only on Wednesday night after she escaped from Kiriona. She is in Waikato Hospital with serious injuries.

"She was [also] subjected to an alleged earlier assault where the offender held her against her will and a firearm was discharged two to three weeks ago," said Mr Lindsay. The woman's two children, aged 7 and 3, were also in the home at the time of the incident.

Mr Lindsay said police were tipped off yesterday morning to the house in Nawton where Kiriona was believed to be holed up.

"Distraction devices were used, however no shots were fired and the offender was not located at the address. A search of the property is continuing and a scene guard is in place," said Mr Lindsay.

Kiriona is 25, 1.75m tall, of medium build and a known methamphetamine user with contacts in the Waikato and Wanganui areas.

He is a patched Mongrel Mob member with a distinctive bulldog tattoo on the left side of his face, is considered dangerous and should not be approached.

Anyone with knowledge of Kiriona's whereabouts or who sees him should ring Detective Senior Sergeant Karl Thornton at Hamilton central police Station on (07) 858-6200 or call 111. Information can also be left anonymously on the Crimestoppers crimeline, 0800-555-111.