(CNN) -- A bus carrying 27 children returning from church camp rolled over Saturday morning on Interstate 35 in Franklin County, Kansas, authorities said.
Eight children were transported by ambulance and 18 others were being taken by bus to their families, Sheriff Jeff Curry said. One child was taken to a local hospital by helicopter.
No other vehicles were involved, he said. The cause of the accident, which is being investigated by highway patrol, is unknown.
The bus was heading northbound on the interstate at the time of the accident, which forced the closure of about five miles of roadway, Curry said. The interstate was reopened in the early afternoon.
Aerial video from the scene showed several children and adults walking along the side of the interstate to ambulances as workers tipped the empty bus back on its wheels.