A 35-year-old woman has been arrested.
A 35-year-old woman from Derby, has been arrested on suspicion of causing death by dangerous driving and driving a motor vehicle when above the prescribed limit of alcohol.
She remains in custody.
Thames Valley Police said the crash took place on the northbound carriageway between junctions 14 and 15 near Milton Keynes at 11.10pm on Monday night.
The collision involved a white Vauxhall Astra and a Scania HGV.
Two children, aged 4 and 10, who were passengers in the Astra tragically died.
Another child passenger in the Astra and the driver were taken to hospital with injuries but have since been discharged.
The driver of the HGV was uninjured.
The motorway was closed in both directions last night and reopened on Tuesday morning.
Please share our appeal for witnesses after a collision which resulted in the deaths of two children.— TVP Milton Keynes (@tvp_mk) August 10, 2021
It happened on the M1 yesterday at about 11.10pm between J14 and J15.
A Vauxhall Astra collided with a HGV. Two children aged four and ten were killed.https://t.co/Fi05nsOLTK pic.twitter.com/hoGLSCZ619
Investigating officer Sergeant Dominic Mahon 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 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."
Their next of kin have been informed and are being supported by specially trained officers.