Watch: Video of a news conference about the school bus collision.
COLUMBIA COUNTY -- Twenty people were hurt when a semi-truck hit a school bus carrying students from a Milwaukee private school Wednesday morning, according to the Wisconsin Department of Transportation.
Four of the injuries are serious, the DOT says. The severity of the other injuries is not yet known.
Two students were released from UW Children's Hospital in Madison after being treated.
The students were from Hope Semper Christian School at 3040 W Capitol Drive.
The crash happened just after 10:00 a.m. on I-39 northbound, near DeForest. The DOT says the semi crashed into the school bus, which was parked on the shoulder of the interstate after pulling over due to a mechanical issue.
Students who were not injured are being transported to the State Patrol Post in DeForest for reunification with family members.
The students were participating in an end-of-year field trip, according to a statement the school posted on Facebook.
"While very scary, our staff and students were blessed by urgent first-responders, local medical attention as well as the kindness and generosity of Deforest Public Schools. Please keep our Semper scholars in your prayers for quick recovery and safe travels to reunite with loved ones," the statement read.