Derby woman Joan Kavanagh has been named as one of the people who was killed following a multi-vehicle crash on the M1.
The accident happened at 5.40am on the northbound carriageway of the M1 on Monday between junctions 11 and 12.
The 89-year-old, of Ashbourne Road, died from her injuries on Tuesday.
Bedfordshire Police are keen to trace the driver of a red car involved in the incident who may have been travelling from Hertfordshire to Northhamptonshire.
PC Andy Ralph of the BCH Roads Policing Unit, said "It was still dark when the incident occurred, conditions on the motorway were slightly misty and foggy and the road was damp.
"Six cars and a motorcycle were involved in the incident which caused fatal injuries to the 36 year old woman passenger travelling in a grey Ford Focus who died at the scene.
"The driver and passengers of an grey Audi Q5 also sustained serious injuries and one woman, aged 90, has subsequently died in hospital from her injuries.
"The 53 year old driver of the Audi and two other women passengers, aged between 89 and 90 years old, suffered a variety of serious injuries to their ribs, abdomen and spines.
"It appears that one vehicle moved suddenly in front of the motorcycle which caused the rider to lose control and fall from her machine.
"Other vehicles following behind attempted to avoid the rider and her motorbike causing several collisions between themselves."
Bedfordshire Police are seeking the drivers of two of a red car and white van involved in the incident for further information which may help piece together exactly what happened.
Anyone with information relating to this collision can contact PC Andy Ralph, at Bedfordshire Police on 101, or text information to 07786 200 011.
Alternatively you can contact the independent crime fighting charity, Crimestoppers, anonymously, on 0800 555 111.
