Two vans carrying about 20 University of Washington students to a conference collided on a central coast highway Friday, injuring four students, two seriously, the California Highway Patrol said.

The vans were driving south side by side on U.S. 101 near Bradley in Monterey County when they crashed into each other around 12:30 p.m., Officer Joel Newby said.

The collision sent one van into the center divide, where it rolled over. Two students were ejected through a broken window and were seriously injured. They were taken by helicopter to trauma centers.

Two other students were taken by ambulance to local hospitals.

Newby says the other van veered onto the right shoulder.

The students, undergraduates from the university's Foster School of Business, belonged to an organization that connects American students with internships abroad as well as foreign students with internships in the U.S., said university spokesman Bob Roseth. In all, there were three vans transporting 33 Washington students to the organization's regional conference in Santa Maria.

The cause of the crash is under investigation.