More than three months after the M5 crash which claimed seven lives and left 51 injured, investigators are still trying to establish why the tragedy occurred and whether it could have been avoided.

The 34-vehicle crash on the northbound carriageway of the M5 near junction 25 at Taunton was the worst accident to hit Britain’s motorways for a decade.

There were no bad weather warning signs on the M5 on the night, November 4 last year, despite the fact that the Met Office had told the Highways Agency of “isolated fog” in the area on the day of the crash. Police are also investigating whether smoke from a nearby fireworks display may have contributed to the pile-up. Some motorists reported smoke or thick banks of fog.

An Avon & Somerset Police spokesman said: “All possible contributory factors to the fatal collision are being fully investigated, including environmental factors, weather conditions, driver behaviour, vehicle condition and distraction.

“The investigation aims to establish what occurred that evening, identify if it could have been foreseen/avoided and what can be done in the future to prevent incidents of a similar nature occurring nationwide.

“This process involves a number of agencies including the local authority and department of transport. In the fullness of time, the investigation findings will be made public.”

Lorry driver Kye Thomas, 38 and from Gunnislake in South East Cornwall, was one of the seven victims. He died along with fellow driver Terence Brice, 55. Both worked for Samworth Brothers – owners of Callington-based Ginsters.

Tonia White, from Taunton, lost her parents, Tony and Pamela Adams, of Newport, South Wales, in the crash. The other victims were Malcolm Beacham, 46, of Woolavington, near Bridgwater; Michael Barton, 67, from Windsor; and Mr Barton’s daughter, Valerie, 30.