Marshall Haynes, Liam Hastings and Josh Bartlett died in the crash

Josh Bartlett, Marshall Haynes and Liam Hastings, all 13, were among seven boys in a Citroen driven by the mother of a boy, who was celebrating his birthday.

The Citroen collided with a Honda driven by Howard Hillsdon, 21, who was also killed, on the A4142 in Oxford.

The remaining four teenage friends and the mother, aged 45, are still being treated in hospital.

I went up to see him at the John Radcliffe yesterday and I'm sorry but I couldn't stay at the bedside, it wasn't him Clifford Wood, whose nephew Aiden Wood, 13, is critically ill

Police said the woman, who appeared to have lost control of the vehicle, crossed the central reservation, colliding with an oncoming car leading to a pile up involving several vehicles.

On Sunday, the families of Josh Bartlett, from Blackbird Leys, Oxford; Liam Hastings, of Rose Hill, Oxford; Marshall Haynes, from Headington, Oxford, and Howard Hillsdon, a former engineering student at Oxford Brookes University, paid tribute to their children.

Howard Hillsdon was described by his family as "outgoing"

The youngsters had been celebrating the 13th birthday of a boy who is still critical in Oxford's John Radcliffe Hospital, along with three of his friends.

The 13-year-old boy's mother was flown to the Great Western Hospital in Swindon, Wiltshire, and remains in a critical condition.

Clifford Wood, whose nephew Aiden, 13, is among those seriously injured at the John Radcliffe, said: "I went up to see him at the John Radcliffe yesterday and I'm sorry but I couldn't stay at the bedside."

He went on to describe Aiden as a "happy-go-lucky, very joyful, very boisterous and very engaging" child.

Mr Wood added: "When something happens like this in the family everybody comes together. It's very hard at the present moment."

Crash vehicles examined

Police have revealed that two of the surviving boys had shown signs of improvement.

Insp Steve Bridges, of Thames Valley roads policing unit, said: "They are in the intensive care unit where their condition is still serious."

He added the police were keeping an "open mind" as to why the Citroen left the southbound carriageway and crossed the central reservation.

All of the vehicles involved in the crash will be examined on Tuesday by investigators and vehicle examiners.

Officers are currently taking witness statements to piece together what happened.

Police are now waiting for the Citroen driver to regain consciousness to gather more information about the incident.