Investigations into the cause of the M5 crash in which seven died will be focused on a nearby fireworks event.
Police said witnesses reported "smoke, not fog" creating "impossible" driving conditions.
A display had taken place at Taunton Rugby Club which is situated alongside the motorway.
Assistant Chief Constable Anthony Bangham told reporters that the investigative phase of the operation was already underway, with a "considerable" number of officers assigned.
"Our main line of inquiry has now moved towards the event that was on the side of the carriageway," he said.
"We do believe that whilst there was fog, and it was difficult conditions in the area, that actually from witness evidence that there was very significant smoke across the carriageway which in effect caused a bank - similar to a fog bank - which was very distracting and very difficult to drive thorugh."
The club's secretary has said they are helping police with their inquiries.
Earlier, police confirmed the final death toll will remain at seven. Officers said their "worst fears" over the M5 accident "have not been realised".
Previously there had been major concerns that the toll could rise as police recovered all 34 vehicles from the wreakage of Friday's crash.
The owner of a local fireworks company told The Mail on Sunday he had turned down the opportunity to stage a display at the rugby club two years ago because of safety concerns.
"It's a very difficult site. My concern straight away was the distance from the motorway," he said.
Asst Ch Con Bangham added that he expected the motorway to be re-opened in time for Monday morning traffic.
Asst Ch Con Bangham said: "Overnight all the vehicles involved in this tragic incident have been removed from the scene.
"Our worst fears have not been realised and the number of those that sadly lost their lives remains at seven.
"Extensive work has been carried out to identify those people and families are being appointed family liaison officers to support them. Formal identification has not taken place - this will happen in the coming days.
"We are now working with our partners to carry out the required work on the carriageway and open the road as soon as it is safe to do so. We thank everyone for their support and patience at this extremely difficult time."
Police said 51 people had been injured and taken to nearby hospitals. Everyone has now either been discharged or is in a stable condition.
According to some reports, four of the confirmed casualties were all travelling in one vehicle.
The devastating crash happened at 8.25pm on Friday in wet and foggy conditions.
Witnesses described a "fireball" engulfing the carriageway. Police said cars were "burnt literally to the ground".
Speed and tailgating will also be factors considered by investigators.
Police have renewed their call for any witnesses to come forward, especially those with mobile phone or camera footage of the incident.
Justine Greening said the Government is to discuss issues arising from one of Britain's worst ever motorway accidents.
"Clearly what we need to do is focus on the NHS work that is happening to take care of the people who have been injured, but also to get the motorway open again for the public as soon as possible," she said.
"We'll also have a debate over any policy issues over the coming weeks."
Plans to increase the speed limit on motorways had been mooted in September.
The stretch of the M5 between junctions 24 and 25 is expected to remain closed for most of today.
Meanwhile, six people were injured in an 11-vehicle pile-up on the M6 near Lancashire on Sunday morning. None of the injuries were life-threatening or life-changing, police said.
:: Anyone concerned about friends or relatives can call an emergency number on 0800 092 0410 .
Police say all other measures should be taken to make contact before this number is dialled.