AUSTIN (KXAN) — Four people were involved in a crash on northbound Interstate 35 that led to a two-vehicle rollover.

Austin-Travis County EMS crews responded to a two-vehicle collision in the 1600 block of northbound I-35 just before 2 p.m. Sunday. Crews helped extricate four patients after both vehicles rolled over.

Two patients have been transported to Dell Seton Medical Center with “potentially serious” injuries; however, officials said those aren’t expected to be life-threatening. The other two patients involved refused medical transport.

Heavy traffic delays are expected on both northbound and southbound I-35 following the crash. Drivers are asked to avoid the area or move over and slow down near crews attending to the scene.