Twenty-five people were taken to hospital after a Delta Airlines flight was hit with extreme turbulence.

The Airbus A330-900, travelling from Salt Lake City to Amsterdam, was forced to divert, landing at Minneapolis-St Paul International Airport.

It is not clear what caused the turbulence. A Delta spokesman said the airline is cooperating with the National Transportation Safety Board in an investigation into the incident.

People were thrown around the cabin during the “really scary” incident, witnesses said.

“They hit the ceiling, and then they fell to the ground,” passenger Leann Clement-Nash told ABC News.

“The carts also hit the ceiling and fell to the ground, and people were injured. It happened several times, so it was really scary,” she added.