A school bus crashed and ended up over an embankment Monday in Kentucky, with 18 children and the driver taken by helicopter or ambulance to hospitals with varying degrees of injury, officials said.

Kentucky State Police were on the scene, and “we are responding swiftly,” Gov. Andy Beshear said in a tweet.

The crash happened on state Route 40 near Salyersville, in eastern Kentucky, the Magoffin County School District said in a statement.

No other vehicles were involved, state Trooper Michael Coleman said. The road was expected to be shut for several hours, he said.

It wasn’t immediately clear what caused the crash.

“We’re really in the beginning stages of the investigation,” Coleman said.