LONDON — Three people have been killed and one person seriously injured when a helicopter crashed Monday during a flight lesson on the Isle of Wight, off the south coast of England.

The Robinson R44 II helicopter had a pilot and three passengers onboard when it crashed just before 9:30 a.m., authorities said.

The operator, Northumbria Helicopters, said its aircraft was involved in a crash during a flight lesson.

The seriously injured survivor was airlifted to the trauma center at University Hospital Southampton.

Eyewitness Leigh Goldsmith was driving when she saw the helicopter spiral down into a hedge, she told the Isle of Wight County Press.

The U.K.’s Air Accidents Investigation Branch said it is sending a team of inspectors to the scene. The cause of the crash is not known.