Five young revellers are believed to have driven around 85 miles before being involved in a crash which tragically left three of them dead.
Eve Smith, 21, Darcy Ross, 21, and 20-year-old Sophie Russon went by car to the Muffler nightclub in Newport, Wales, where they stayed until around 11.15pm on Friday night.
They are thought to have then met two men - Rafel Jeanne, 24, and 32-year-old Shane Loughlin - and left in a white Volkswagen Tiguan, driving 36 miles to Trecco Bay caravan park in Porthcawl.
Ms Russon's mum, Anna Certowicz, reportedly said her daughter hadn't known the two men before that night.
They then travelled 28 miles back to Cardiff, where they are said to have dropped off an unnamed man.
They were last seen inside the car at 2am on Saturday in CCTV footage taken at a petrol station in the Llanedeyrn area of Cardiff.
Ms Ross and Mr Jeanne had also shared a Snapchat post of themselves together just hours before the deadly crash.
The wreckage was discovered two days later, in the early hours of Monday, after the car came off the A48(M) in St Mellons, Cardiff and crashed into trees.
While their precise route is not known, the distance between the night club, caravan park, petrol station, drop-off point and where the car was found adds up to approximately 85 miles.
The Independent Office for Police Conduct (IOPC) has since announced that it is "urgently" carrying out an assessment into Gwent Police and South Wales Police's handling of the case.
A spokesperson said: "In relation to the Cardiff car crash where three people were killed, we are urgently carrying out an assessment of referrals received yesterday from Gwent Police and South Wales Police to determine what action may be required from us."
Last night, both forces said they had referred themselves to the watchdog "in line with normal procedure".
A missing person report was filed with Gwent Police at around 9pm on Saturday, reports The Telegraph.
It was not until the next day, at around 11am on Sunday, that Gwent Police released their own public appeal.
Ms Certowicz launched her own desperate search for her daughter, Ms Russon, who is thought to have laid semi-conscious in the wreckage while calling for help for two days.
She told the Daily Mail: "It's too awful to imagine what she went through trapped in the car in the dark until it got light and then dark again over two days.
"Sophie was lying there for all that time, they could all have been found much quicker if the police had started searching straight away."
Ms Smith, Ms Ross and Mr Jeanne died in the accident, while Ms Russon and Mr Loughlin remain in a critical condition in hospital.
Friends of the five claim they found the vehicle - while police insist it was located by a helicopter.
A vigil is planned for 6pm today at the scene of the accident, according to posts on social media.
Tributes have been paid on social media with family members confirming their loved ones had died.
The sister of Eve Smith paid tribute to her in a post on Facebook.
"My beautiful little sister I've cried laughed and fought with you every week, but I've never been without you," she said.
"We always said, 'I got you always' but now I'm sat here feeling so empty because you're not here with me anymore, and I can't accept this.
"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."
A friend of Miss Ross and Miss Smith wrote: "I don't really have the words right now.
"Darcy Ross I'm going to miss you little gypsy girl. You were one of a kind, I'm going to miss trying to 'life coach' you as you would've said. You were a real ray of sunshine especially on my bad days.
"Eve Smith you were truly a beautiful young girl, who's heart was made of gold just like your sister's, give her a big hug for me and hold each other tight until the day we all have our turn and reunite."
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 the thought of them all there all of that time.
"Many times I have driven past, it just makes me so sad and to how helpless our Shane Loughlin must of felt trapped inside.
"Wish Sophie a speedy recovery and I send all my love and strength to all the families involved."
Photographs from the scene show large green fencing and tarpaulin has been erected around the crash site, which is among trees.
People have also started arriving to leave floral tributes to those who died.
One wrote: "Fly high. You're in a better place now. This was a last thing we expected. I know you're still partying up there. Have one for me lol."
Speaking at the scene, a friend of the three girls claimed it was members of the public searching who found them and not the police.
Tamzin Samuels, 20, said: "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.
"They were really popular girls, the life of the party, and it was really out of character for them to do what they did, which is why we knew something was wrong."
Miss Samuels, a carer from Dyffryn, paid tribute to her friends.
"They were the life of the party. Darcy was known as a wild child, loved life and lived life to the fullest and she didn't care what anyone thought about her. She was great," she said.
"Eve had a smile that could brighten a room as soon as she walked in. A real feisty, independent girl, but everyone loved her just as much.
"I didn't really know the boys and one of our friends who is recovering, we just really hope for her on the road to recovery."
South Wales Police (SWP) said on Monday evening that their investigation into the incident is continuing and confirmed the names of the victims.
