Rebecca Lee, Ellie Chambers and Clifford Jones were killed in Saturday's crash
A 24-year-old man is in custody arrested on suspicion of causing death by dangerous driving following a car crash where three teenagers died.
Rebecca Jane Lee, 18, died with best friend Elin Rowlands, 15, also known as Ellie Chambers, and Clifford Thomas Jones, 17, in the crash on Anglesey.
The crash early on Saturday has left a 17-year-old girl in a "critical but stable" condition in hospital.
Floral tributes continue to arrive at the scene of the tragedy.
North Wales Police described the scene which confronted their officers, where the Citroen C2 car left the A5 at Menai Bridge shortly before 0100 GMT on Saturday and ran into a tree, as "horrific".
They say road and weather conditions were good at the time and their investigations were concentrating on why the vehicle left Holyhead Road, which has a 30 mph speed limit.
While the investigations continue, the family of those who died have paid tribute to their memory.
Flowers left at the crash scene in Menai Bridge
Rebecca's family said they would never get over her loss.
In a statement, Rebecca's sister Kim Hughes said on behalf of the family: "Everyone around Bangor knew Becky Lee. She was a lovely girl and a great little character.
"She will be missed so much by her family and all her friends.
"Everyone loved Becky and we will never get over losing her. We would like to thank everybody for their kindness at this terrible time.
"Our thoughts are also with the families of the other victims."
According to her profile on a social networking site, Rebecca was expecting a baby later this year.
It has emerged that Elin Rowlands was one of triplets.
Her family said they were devastated over a "happy-go-lucky, smiling bubbly" girl who was "friends with everyone".
Elin's sisters, Amy and Tesne, wrote a verse on Saturday night after they learned of her death.
It reads: "We will always be three / And three we go on / In our hearts and our minds / Forever we will be one".
In a statement, her family said: "Elin was one of a set of triplets. She leaves a mum, stepdad, her two sisters and three brothers and a devastated extended family.
"She was a happy-go-lucky smiling bubbly little thing and was friends with everyone. She worked at the local store and post office and everyone is gutted at this news.
"Elin's ambition was to study at Coleg Menai on a health and social course with a view to becoming a nursery nurse.
The tree hit by the Citroen C2 fell onto a parked car
"She loved and was great with kids, in fact she was great with everyone. We will miss her so much".
Clifford Jones's family issued a statement via North Wales Police, saying he would be "sorely missed by his family and all his friends".
They said: "Even though Cliff was a young man he was very grown up and really looked after us all, he would help anyone.
"Not a day goes by when we wish that you were here, it's like a bad dream and we will wake up and see you there with your funny smile and jokey way."
Elin was from Bangor, Gwynedd, as was Rebecca, while Clifford was from Malltraeth, Anglesey.
A 17-year-old girl, named locally as Stacey Williams, and the 24-year-old male driver were injured when the car left the road and remain in hospital.
The Reverend Phillip Huws, vicar of Llanfair PG and the area's dean, said people were still "dealing with so much loss of young life and potential".
He said: "They're seeking some sort of answers and at present there are just no answers.
"When the police investigations are over and they can give some sort of explanation then people will find some sort of closure."
North Wales Police said no other vehicle was involved, although the tree which the car struck then fell on to a parked car.
Anyone with information can contact 0845 607 1001 (English language line), 0845 607 1001 (Welsh language), text 66767 or e-mail email@example.com.