The Independent Office for Police Conduct (IOPC) has launched an investigation into two police forces over the search for missing victims of a deadly car crash in Cardiff amid allegations they did not take matters seriously.

Eve Smith and Darcy Ross, both 21, and Rafel Jeanne, 24, died in the collision, while Sophie Russon, 20, and Shane Loughlin, 32, remain in a critical condition after a Volkswagen Tiguan they were in left the A48(M) in Cardiff and hit trees in the St Mellons area of the city.

Officers believe the car was involved in a collision and left the road some time later, but further investigations are needed to establish an exact time.

The group had been to a social club in Maesglas, Newport, on Friday and are thought to have then travelled 40 miles to the Trecco Bay area of Porthcawl.

After failing to go home, the five were reported missing by their families.

A vigil was held at the crash site on Tuesday evening where around 1,000 people gathered, lighting candles and flares while others rode mopeds, motorbikes and quad bikes around the roundabout.

A firework display lit up the sky above St Mellons for around 30 minutes while family and friends looked on.

Rafel’s sister, Ffion Actie, told Sky News at the vigil she feels “disappointed” police did not act sooner.

She said: “I heard the girls’ mums had contacted (police) but it had taken several hours (to respond).

“I feel they should have acted straight away.”

Ms Actie added: “I like to think that if (police) got there sooner, it would have been a different outcome.”

Rachel O’Neill, 37, from Rumney, attended the vigil with her daughter Molly.

She told the PA news agency: “It’s been heartbreaking to think that they were there for so long, for 46 hours, and that they were found by people and not even the police.

“It’s absolutely disgusting, and you just don’t know. There could have been some lives saved if they had moved faster.”

They said they knew Mr Jeanne and Mr Loughlin, and Molly O’Neill added she was friends with Mr Jeanne’s sister.

Another woman at the vigil, who did not want to be named, told PA there is “a feeling of anger” among mourners.

The woman, from Llanrumney, said: “There’s a sense that if we had left it to the police and the public had done nothing, that they’d probably still be in that car in there. It’s just sad the police didn’t think they were a priority and thought they were partying.”

The first call reporting the victims as missing was made to police at 7.34pm on Saturday, while further reports were made up until 5.37pm on Sunday.

Hundreds of people took part in searches but Gwent Police did not issue a public appeal for help until 11pm on Sunday.

David Ford, IOPC director, said: “After careful assessment of referrals from Gwent Police and South Wales Police, we have decided to independently investigate how police responded to the missing person reports.

“We will be examining what information police had, the grading given to any risk assessments and the steps taken by police to locate the missing people prior to the Volkswagen Tiguan being found just after midnight on Monday.

“We will also consider what communication took place between the two forces and whether police action was appropriate and followed relevant policy and procedures.”

Police have confirmed the group were last seen at about 2am on Saturday in Pentwyn, Cardiff.

In a joint statement, Gwent Police and South Wales Police said a helicopter was asked to search an area of Cardiff at 11.50pm on Sunday.

The forces added that Gwent Police officers on the ground had sight of the car at 12.02am on Monday and South Wales Police created a log at 12.15am.

But members of the friends’ search party, Matthew Pace, 45, and his son Lewis, 26, told Sky News they found the car shortly before officers arrived after seeing tyre marks leading off the road and into a wooded area.

Tamzin Samuels, 20, a friend of the young women and who helped in the search effort, 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.”

Two women who were friends of the Loughlin family questioned the police response.

They said: “The police were terrible. I don’t think they took it seriously.”

“The families said it was out of character for them to go missing and the police should have listened to them.”

They added: “Shane’s mum was up all weekend worried sick.

“The boys from Cardiff, all their friends were driving around looking for them. It was those people looking who found them, not the police.”

Tributes to those who died have been paid on social media.

A friend of Mr Loughlin posted: “I’m so proud of us all pulling together out there searching for our dear friends last night.

“It’s heart breaking what’s happened to Rafel Jeanne and those two girls. My body is still shaking and I can’t stop being sick (at) the thought of them all there all of that time.”

Ms Smith’s death comes eight years after her sister Xana Doyle, 19, was killed in a car crash. The driver, who was twice the drink-drive limit, was prosecuted and Ms Smith took part in a Sky TV documentary about the incident and campaigned for tougher sentences.

Another sister paid tribute to her in a Facebook post.

“I know you’re safe up with there with our beautiful sister Xana but I was never ready to let you go, my body is aching without you,” she said.

In a statement, Ms Smith’s family asked for their privacy to be respected.

They added: “We want to allow Gwent Police and South Wales Police the time and space to investigate the matter in a thorough and professional way and to enable the Independent Office for Police Conduct thereafter to come to their own conclusions.”

Gwent Police’s Assistant Chief Constable Mark Hoborough and South Wales Police’s Assistant Chief Constable Jason Davies said their thoughts are with the victims’ families.