Williams said on Wednesday they were investigating the cause of a heavy crash suffered by Nico Rosberg during testing in Barcelona in the morning but the team pointed out that it happened early in the day when the track was still damp from heavy rain on Tuesday.

"Nico went off on his first run and had a crash that resulted in heavy chassis damage," said technical director Sam Michael.

"Nico's fine, however the damage cannot be repaired at the circuit so the test team is now returning to the factory."

The German was unhurt but was taken to hospital in the Spanish city as a precaution before being allowed to go home.

Japanese test driver Kazuki Nakajima hit the tyre barriers on Monday, badly damaging the right side of the car and forcing the team to fly out more parts.