Police are focusing on 10 names in their bid to solve the Kirsty Bentley murder cold case.
Out of about 80 pieces of information, police received after a $100,000 reward was posted in late July, there were 10 people being prioritised for further investigation, Detective inspector Greg Murton said.

He noted they had some "interesting links and connections".

"It's a range. They're people who have been mentioned before or people who lived around the area that were not looked at."

There were also 14 nominations that required no further action, and about 40 that required tidying up.

The reward was for any information or evidence leading to the identification and conviction of the person or people responsible for the Ashburton teen's death.

Murton said there was nothing obvious yet and it was too early to tell whether the nominations would yield anything concrete.

The Ashburton 15-year-old was last seen alive on the afternoon of December 31, 1998, when she left home to walk her labrador cross, Abby.

Jill and Sid Bentley, parents of murdered Kirsty Bentley, at home in Ashburton. Also picture is their dog Abby, who was with Kirsty when she disappeared. Photo / John McCombe

Abby was found the next day tied to a tree near the Ashburton River along with a pair of Kirsty's underwear and boxer shorts.

Her body was found 17 days later in the Rakaia Gorge.

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The investigation initially focused on Kirsty's father, Sid, and brother, John, but both denied any involvement.

Sid died of cancer in 2015, while John now lives in the United Kingdom.

Murton, who has looked over the case for eight years, ruled them out of his investigation.

His primary theory was Kirsty was abducted and killed by a stranger, who lived locally, either smoked or grew cannabis and knew the Rakaia Gorge area.

Greg Murton. Photo / Jason Oxenham

While he was continuing to review the tips alone, Murton said he would bring other detectives on board if inquiries needed to be made.

There had been a "great response" since the reward was posted, he said.

It will remain in place for another three months.

Immunity from prosecution could be considered for any accomplice not being the main offender.

Anyone with information should phone police on 105 and reference Operation Kirsty, or call Crime Stoppers anonymously - 0800 555 111.