A 26-year-old man from the Spalding area was arrested after three people died in a collision on the Fletton Parkway in Peterborough.
He has since been de-arrested and remains in a stable condition in hospital.
Police were called to a collision involving a Ford Ranger and a Renault Megane at the slip road to Stanground on the westbound carriageway just after midnight on Sunday, April 14.
All three occupants in the Megane died at the scene.
Cambridgeshire Police has since named them as sister and brother Jana Kockova, 21, and Tomas Kocko, 19, both of Hinchcliffe in Peterborough. Jana’s fiancé Marko Makula, 22, of Reeves Way in Peterborough also suffered fatal injuries.
The driver of the Ford Ranger from the Spalding area was arrested on suspicion of causing death by dangerous driving and driving while under the influence of drink and/or drugs. He has since been de-arrested and remains in a stable condition in hospital.
Anyone with information about the collision should contact Cambridgeshire Police on 101 or online here quoting incident 2 of April 14.