A semitrailer towing a trailer flipped onto its side just after noon on Wednesday on State Route 18 in a three-car accident east of Issaquah-Hobart Road.

The semitrailer had been traveling westbound on Route 18 when it managed to move into the eastbound lane, striking both a dump truck and a car. The car was barely damaged, but the dump truck “got hung up on the guardrail,” Washington State Patrol Trooper Chris Webb said.

He noted the car was carrying three passengers at the time of the crash. They, along with the three drivers, went to the hospital with minor injuries.

The overturned semi and trailer caused a buildup of traffic on Route 18. As of 3 p.m. on Wednesday, the road was still blocked; Webb estimated it would stay this way until at least 5 p.m.

Authorities are still investigating why the semi drove into the opposite lane in the first place.