At least two people suffered minor injuries when an employee shuttle clipped a passenger airplane taxiing for departure at Chicago O’Hare International Airport on Friday, officials said.

The bus and plane made “minor contact,” and the injuries to two people were characterized as very minor, said Chicago Fire Department spokesperson Larry Langford.

The two were taken to medical facilities, he said.

American Airlines said that the ground vehicle was one of its employee buses and that six of its team members on board were being evaluated at a hospital. No injuries were reported among those on the aircraft, it said in a statement.

It was not immediately clear whether the airline’s total included the two mentioned by the fire department.

The plane, a Bombardier CRJ-200 operated by Air Wisconsin Flight 6209, was taxiing ahead of takeoff when the collision took place about 7:20 p.m., the Federal Aviation Administration said in a preliminary statement.

American described the plane as one of its American Eagle flights operated by Air Wisconsin. The carrier said those on board were offered a different aircraft flying to their destination, Dayton, Ohio, later in the evening.

American and Air Wisconsin have a partnership for regional service.

It’s not clear why the bus and plane were so close to each other, and cause was unavailable.

Langford said one of the vehicles clipped the other, though it wasn’t initially clear which one struck the other.

The FAA said the collision was under investigation.