Police believe that the driver killed in the major accident on the M27 was a man in his 40s.
His Ford Focus collided with a lorry and caught fire.
The man died at the scene and officers are still carrying out enquiries to confirm identity and contact all next-of-kin.
The lorry driver, a 53-year-old man from Wiltshire, was shaken but otherwise uninjured.
The other vehicles involved were black Citroen C5 driven by a 53-year-old man from Hedge End, a silver Vauxhall Zafira driven by a 29-year-old man from Eastleigh and carrying four passengers: a 25-year-old woman and three young children and a black Honda CR-Z driven by a 39-year-old man from Swindon.
Sergeant Adrienne Jerram from the Serious Collision Investigation Unit said: ‘This is a very complex investigation into a serious collision in which one person died.
‘We have spoken to all the drivers involved and at this time we are focussing on establishing the exact sequence of events leading to the collision as well as which vehicles were in contact with one another.
‘A lot of people were driving along that stretch of the motorway yesterday morning and I’d like to thank everyone who has come forward with information so far. I’d still like to hear from you if you’ve not yet spoken to us and can help with our enquiries, especially if you witnessed the collision or saw any of the vehicles involved.
‘In particular, I’m aware there are video clips of the incident recorded on dashboard cameras from vehicles passing by and I am very keen to hear from anyone who can us provide with this footage.’
Anyone with information is asked to contact the Serious Collision Investigation Unit at Eastleigh police station on 101.
For alternative ways of contacting the police in non-urgent situations, please visit the Contact Us page of our website.
The crash happened on the eastbound stretch of the M27 just before junction 9 for Whiteley. Part of the motorway was closed for most of yesterday and overnight.