Detectives are using new technology to probe the area close to the Hanover Street flat in Portadown where Caroline was living with her boyfriend before her disappearance more than 20 years ago.

The 19-year-old, who was originally from Newry, Co Down, had been living in the town for two years and previous searches in the area close to her home proved fruitless.

"We have received a number of pieces of information some quite recently to suggest that Caroline may be buried here," said Detective Chief Inspector Gary Crawford, who is in charge of the investigation.

Diggers are clearing shrubbery away from the site and probes put as deep as five metres into the ground to determine if there are any human remains. It is technology that has never before been used in Northern Ireland.

"We will have a range of assets on site to assist us in what could be a protracted operation. These will include a body recovery dog, earth moving machinery and specialist scanning equipment," DCI Crawford explained.

"We believe Caroline has been murdered and we believe her remains are buried somewhere in this vicinity."

But the police chief added he believes some people in the Portadown area know what happened to Caroline.

"We need those people to examine their conscience come forward and tell police where exactly Caroline is.

"We are determined to try and bring this investigation to a close if we possibly can," he added.

The Graham family have shared a previously unreleased picture of Caroline, in the hope that someone might come forward with information about her disappearance and death.

"The last 23 years for Caroline's parents have been absolutely horrendous," said DCI Crawford.

"They just want it to come to an end and they want people to help the police, to tell us where Caroline is buried, so they can finally bury Caroline."

In 2000 one person was arrested in connection with Caroline's disappearance but no charges have ever been brought.

In August the PSNI opened a new murder inquiry.