Sophie Russon, 20, Eve Smith, 21, and Darcy Ross, 21, from Newport, and Rafel Jeanne, 24, and Shane Loughlin, 32, from Cardiff, were all reported as missing over the weekend.

Shortly after midnight on Monday, nearly 48 hours after they had last been seen, their VW Tiguan was found crashed off an A48 roundabout in St Mellons.

Ms Smith, Ms Ross and Mr Jeanne had all died, and Ms Russon and Mr Loughlin had suffered "serious injuries".

South Wales Police said "the five individuals were the subject of enquiries by Gwent Police following a missing person report made during the evening of Saturday, March 4".

"A subsequent missing person report in respect of one of the individuals was made to South Wales Police on Sunday, March 5," the force added.

But the speed and scale of the search for the missing group has been criticised by relatives and others.

Anna Certowicz, the mother of Ms Russon, told the Daily Mail that Gwent Police did not take her seriously when she reported her daughter missing, after she lost contact with her in the early hours of Saturday.

“They kept saying she's 20 and they are all probably out partying," she told the Daily Mail, adding: “We all knew it was something serious, all their phones went off line at the same time.

“But the police didn't listen, they didn't want to know, it's disgraceful."

On the weekend, Lauren Doyle, a sister of Ms Smith, said the group's disappearance had been reported to the police on Saturday, but that she had been told it was "low-risk" at this time and that more time would have to pass before that status was changed.

Dimitris Legakis. Athena Picture Agency (Image: Dimitris Legakis. Athena Picture Agency)

At the scene on Monday, mourner Tamzin Samuels, 20, told the PA news agency: "I do think the police could have done a lot more in putting the helicopters out earlier.

“They only posted the appeal an hour before the girls were found. We found them before the police found them – we rang the police.

“The search party found the girls before the police found the girls.

“I think that speaks volumes really, they had all that equipment, and we had cars when we were looking."

South Wales Police has suggested emergency services found the group's car.

And another mourner, Thomas Taylor, told PA: "I feel for the families because from what I can see from the reports they did have a feeling something was wrong and they were flagging it up. Their instincts were correct."

South Wales Police and Gwent Police have referred the case to the IOPC, the police watchdog, in line with "normal procedures".

Neither force responded to request for comment on the specific concerns outlined in this article, but in a joint statement issued on Tuesday afternoon, said the families of the victims "continue to be supported by specialist family liaison officers".

Assistant Chief Constable Mark Hobrough of Gwent Police said: “This is an extremely sad situation, and our thoughts are with the families and friends of each of the young people involved.

"We will continue to support the investigation and would ask members of the public to refrain from speculation during this period.” 

Assistant Chief Constable Jason Davies of South Wales Police said: “Our thoughts continue to be with the families and all those affected by this tragic incident.

"Specialist officers are carrying out a detailed investigation to piece together what has happened.

"Family liaison officers are supporting the families involved at what must be a hugely difficult time for them.”