Officers said a lorry voyaging southbound smashed through the focal reservation and hit no less than two vehicles heading the inverse way.
A lady and two kids were additionally harmed in the crash and taken to doctor’s facilities in Bristol, where they are in a perilous condition.
Crisis administrations were called soon after 14:30 BST to intersections 15 and 14 in Gloucestershire.
The lorry driver was taken to clinic to be looked at as a precautionary measure.
The motorway stays shut in the two headings and drivers have been made a request to maintain a strategic distance from the range, while Avon and Somerset Police said it would stay close “for a lot of time”.
Director Simon Ellis of Avon and Somerset Police said the protect and recuperation operation was “careful work” and that various preoccupations stayed set up.
“Our need is to guarantee the casualties’ closest relative are advised and upheld, and in addition the progressing administration of the scene, and this imperative work is continuous,” he said.
Supt Ellis expressed gratitude toward the crisis administrations, and individuals from the general population who “valiantly went to the guide of those included” in the impact.
Expressways England cautioned of “long postponements” and prior said there was a six-mile line northbound between intersection 18 for Avonmouth and 16 for Almondsbury.
There were additionally three miles of “caught activity” inside the police cordon, it included.
Cardiologist Dr Amer Hamed was in an auto voyaging “10 to 20 seconds behind” when the crash happened.
He was one of the first at the scene alongside a passing GP and different doctors to help a harmed lady who was in one of the autos.
Paramedics touched base on the scene around six minutes after the fact and the lady Dr Hamed had been helping was taken away by emergency vehicle to healing center.
He stated: “There was a lorry included and no less than two different autos. One was completely wrecked and another had flipped over.”
He said drivers who had been stuck on the carriageway for a few hours were in effect “extremely supportive”.
“Individuals are helping as much as they can,” he said.
“A few people offered us water and one man left his auto to give nourishment. We will be stuck here for a couple of hours yet.”
The most striking thing about the scene is the practically entire hush here.
Investigating the extension, the police, fire and emergency vehicle groups are persistently doing their work at a significant irritating scene.
The lorry that has slammed has hit what M5 workers will know as a well-known historic point, a windsock beside the street. In any case, nearby that are a few autos squashed from the effect.
On the opposite side of the extension, drivers quietly hold up with some anxious to offer assistance. I caught one inquiring as to whether any petition bolster was required. While others converse with cops about the misery of what has happened.
South Western Ambulance Service said it was called soon after 14.30 BST.
A representative stated: “We have 13 assets at the scene including the basic care group and the perilous range reaction group.”
Avon Fire and Rescue Service sent six vehicles.
Interstates England said the “early desire” is that the M5 “will stay shut in the two bearings late into tonight”.
It included drivers the M4 wanting to join the M5 northbound were not able do as such.