A police watchdog is "urgently" carrying out an assessment into two force's handling of a fatal car crash which killed three people and left two others seriously injured.
Eve Smith, 21, Darcy Ross, 21, and Rafel Jeanne, 24, died in the accident while Sophie Russon, 20, and Shane Loughlin, 32, survived but remain in a critical condition.
All five were in a Volkswagen Tiguan that came off the A48(M) in Cardiff and crashed into trees.
Ms Russon is said to have laid semi-conscious in the wreckage while calling for help for two days.
Her mum, Anna Cerowicz, claimed she phoned Gwent Police 10 times on Saturday, but was apparently told that Ms Russon was "probably out partying".
She said the force only put out its own public appeal the next day, shortly after 11pm on Sunday.
Both South Wales Police and neighbouring force Gwent Police said they have referred themselves to the Independent Office of Police Conduct (IOPC) "in line with normal procedure".
And in an update this morning, the IOPC said it is "urgently carrying out an assessment" of the referrals which were made yesterday.
A spokesman 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."
The three women were last seen in Cardiff in the early hours of Saturday having travelled there from Porthcawl. They had earlier been in Newport and were reported missing to Gwent Police.
The two men, who were from Cardiff, were also reported missing by their families.
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."
The car was discovered shortly after midnight on Monday in the St Mellons area of the capital, South Wales Police said.
It is understood a helicopter searching for the car found it.
Three people were found deceased while two others were taken to hospital with serious injuries.
Officers believe the car was involved in a road traffic collision and came off the A48(M) but it is not clear exactly when that happened.
The road had been closed in both directions, near to the Cardiff Garden Centre, by the police.
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."
Another said: "RIP Darcy."
And second a tribute left by the same person said: "RIP Eve."
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.
