It was around 04.30 that the three trucks collided on the E6 south of Tanumshede, at the height of Solhem.
Four people were injured, one of whom was a woman very seriously. Several people have had to be cut out of the trucks, the police write on their website.
According to the rescue service, it must be very slippery at the site.
The police investigate crimes
One of the trucks is on its side blocking the road in the northbound direction. In addition, both fuel and cargo have spilled over the road.
– The road is still closed in both directions, says Johan Eklund, alarm and line operator at the rescue service, at 06.45.
According to the Swedish Transport Administration, road users are being diverted via the old E6, route 920. The continued rescue work is expected to take several hours.
The police are investigating the accident as a traffic offense with the criminal classifications of causing bodily harm and negligence in traffic.