The family of a missing Co Down woman have appealed for information on the location of her remains so that they can finally lay her to rest beside her mother.

It has been 16 years since 25-year-old Lisa Dorrian from Bangor disappeared.

She was last seen alive at a party in Ballyhalbert Caravan Park on 27 February 2005.

There have been extensive searches of the area, including of a disused airfield in 2019.

Lisa's sister Joanne Dorrian said they have received multiple tips, but they believe a small group of people are keeping the exact location a secret.

"Police believe that Lisa is down there, we do believe she is down there but it's such a vast area," she told the PA news agency. "It sounds so simple, 'she's on the caravan park, just find her', but it's really difficult even with all the technology unless we know where she is.

Her father John said all they are waiting for is someone to talk.

"From the very first day it was said by police that they needed someone to talk, and that's what we are waiting for," he said. "We would appreciate any information, any small bit of information.

"This is still an ongoing investigation, it is still current and we have good police officers working on it."

Joanne said the family's life is now in two parts; before Lisa went missing and after.

"It's a benchmark for how we reference things, it has changed us as people," she said. "My youngest sister Ciara was eight at the time, she is now 24, that's the passage of time from her being a young child to a fully grown women and we are still campaigning for justice and to find Lisa."

Joanne believes Lisa's disappearance led to their mother Pat's death in 2015.

"It was really tragic for the family," she said. "Another blow between Christmas and New Year, an already difficult time of year now compounded by not having her but we take solace that they are together again now.

"It's our duty on earth to find Lisa and be able to bury her with mum."

With no grave, Joanne says the closest the family can feel to Lisa is at a cherry blossom tree planted in her memory.

In the years that Lisa has been missing it has grown into a 15 foot tree.

John said the tree and a memorial bench were put in place by Lisa's friends when she first disappeared.

"The tree blooms every year and it is somewhere we can come to, to remember Lisa which we do regularly," he said.

Joanne said that while it is a comforting place to visit in some ways, it also reminds them that they do not have a grave to visit.

"So sometimes it is very difficult to come here, because it reminds you that this is not Lisa's resting place yet it is the only place we have to come and remember her," she said. "But the grounds are beautiful and when the cherry blossom is in bloom, it is lovely, it's bright pink and a nice reminder of Lisa and the life that she lived."

Detective Superintendent Jason Murphy said he has not given up hope that Lisa's body will be found and her family will get justice.

"She was last seen alive in the caravan around 10pm on Sunday February 27," he said. "I believe she was murdered that night or in the early hours of the following morning.

"There is nothing to suggest that Lisa came to harm at the hands of a stranger, I believe she knew her killer.

"My focus is very, very clear and that's on the recovery of Lisa and justice for Lisa's family and I've not given up hope that we will achieve either or both."

Anyone with information should call detectives on 101 or talk anonymously to the independent charity Crimestoppers on 0800 555 111.