A semi-truck rolled over and spilled its load on Interstate-80 near Dexter today, then caught fire — sparking a grass fire along a stretch of interstate. Troopers closed Interstate-80 in both directions and diverted traffic around the accident site, which is about 34 miles west of Des Moines. One lane of east-bound traffic on I-80 has just re-opened in the area. Westbound traffic is still being diverted.