MONROE — All lanes of Highway 522 near the Snohomish River Bridge were shut down Tuesday afternoon as the State Patrol investigated a two-car collision.

At 3:50 p.m., a Toyota Corolla heading east on the highway apparently crossed the center line just before the bridge. A Ford Taurus traveling west was struck head-on, said Lt. Steve Burns.

The Toyota driver sustained serious injuries and was taken by helicopter to Harborview Medical Center in Seattle. The Toyota driver wasn't hurt but was taken to Valley General Hospital in Monroe as a precaution, Burns said.

Burns said it's unclear what caused the driver to cross the center line. Drugs and alcohol do not appear to be factors in the crash, he said.