The children, aged four and 10, died in the collision between junction 14 and 15 near Milton Keynes on Monday night. A 35-year-old woman has been arrested.

A woman has been arrested on suspicion of drink-driving after a two children died in a crash on the M1.
The children, aged four and 10, were passengers in a white Vauxhall Astra which was in collision with a Scania HGV.
Another child passenger and the driver of the Astra were injured and taken to hospital but have since been discharged. The HGV driver was not injured.
The collision took place on the northbound carriageway between junctions 14 and 15, near Milton Keynes, at around 11.10pm on Monday.
Their next of kin have been informed and are being supported by specially trained officers.
Thames Valley Police said a 35-year-old woman, from Derby, was arrested on suspicion of causing death by dangerous driving and driving a motor vehicle when above the prescribed limit of alcohol.
We are appealing for anyone who may have witnessed this collision or anyone who may have dash-cam footage that may have captured what happened, or either of the vehicles prior to the collision to please get in touch. You can make a report by calling 101 or online, quoting reference 43210356500.
Sgt Dominic Mahon
She remains in custody.
Investigating officer Sergeant Dominic Mahon, of the serious collision investigation unit at Bicester, Oxfordshire, said: My thoughts remain with the family of the two children who sadly died at this extremely difficult time.
We are appealing for anyone who may have witnessed this collision or anyone who may have dashcam footage that may have captured what happened, or either of the vehicles prior to the collision, to please get in touch.