HELSINKI — A landslide in western Sweden caused a huge sinkhole on a major highway to Norway early Saturday, and three people were injured when their cars and a bus skidded off the road, police said.

Photos and video footage showed a sinkhole 500 meters (1,640 feet) wide that had opened up on the E6 highway, which runs from southern Sweden to Norway, not far from Sweden’s second largest city of Goteborg.

Police said at least four cars and a bus skidded off the road and crashed, and three people were hospitalized. Several buildings and facilities were damaged, including a Burger King restaurant.

Swedish emergency services received alarm at 1:45 a.m. that a substantial part of the E6 had collapsed in Stenungsund, police spokesman August Brandt told Swedish public broadcaster SVT.

Emergency officials were searching with specially trained dogs and staff to ensure there were no people trapped in the debris.

The cause for the landslide wasn’t immediately known. Swedish media said the area has seen substantial construction activities involving blasting and excavation work. A large amount of rain also has fallen in the past few days.

Footage taken by a drone showed that a crack on the E6 had appeared after the start of the construction of a business park, Swedish newspaper Dagens Nyheter said.

Swedish police started a preliminary investigation.