The M5 Southbound between junctions 25 and 26 (Taunton) is expected to stay closed until at least 11am.
It's following a crash in which a man in his 20s died. Another two people have been taken to Musgrove Park hospital in Taunton in a life threatening condition. All were travelling in the same car.
Police are appealing for witnesses to the crash.
Motorists are being advised to take alternative routes.
More top news
Friends of a woman with a one-in-a-billion combination of two life-threatening illnesses are trying to raise £70,000 to send her to America
Investigations have begun into what caused a enormous fire to rip through student accommodation in the centre of Bristol.
Kingsholm are opening their gates to rugby fans for the final few games of the Rugby World Cup. The tournament brought in around £40m.