The wrecks took place between Gothenburg and Kungsbacka, with one vehicle reported to have left the scene.
According to Swedish emergency services in Halland County in western Sweden, a total of 13 people were taken to hospital in ambulances. It remains unclear exactly how serious their injuries may be.
Eight people were injured in a three vehicle wreck shortly after two others were injured in an apparently unrelated crash a short distance away.
Yet another accident occurred a short time later in the vicinity of the first crash, between Sandsjöbacka and the Kungsbacka North exit off of the E6.
“We're trying to scrape together all the ambulances we have,” an emergency services operator in Halland told the TT news agency.
According to police in Halland County, one driver left the scene of one of the crashes.
“It's still unclear from which accident. But the car apparently drove off at the Kungsbacka North exit. And shortly thereafter drove off the road near Hede by the old Gothenburg Road. We just located the car,” Leif Berglund of the Halland police told TT.
The E6 motorway was closed off in both directions as crews attended to the injured and worked to clear the roadway, causing long traffic jams.
Authorities are also somewhat mystified about the causes of the accidents. According to Sweden's National Transport Administration (Trafikverket), road conditions near the scene of the accidents were good, with no slick patches having been reported.
“No, it's not slippery. We've had people out and they can stand. Even information from emergency crews indicate that it's not slippery,” said Bernt Sveitz of the road administration's western regional office to TT.
“Right now we don't know what might have caused the accidents. Maybe someone was blinded; the sun was up but at a low angle. But that's just speculation,” he said.