LONDON (AP) _ The Royal Air Force has restricted flights of its 32 Chinook helicopters and launched an investigation into two crashes of the twin-rotor aircraft this week, the air force said Thursday.

The crashes Monday and Tuesday resulted in only minor injuries to those on board, but as a precaution few, if any, flights of Chinooks would take place for now, the spokesman said.

''As a precautionary measure, RAF Chinook flying is being restricted to that which is operationally essential until the causes of the two accidents have been identified,'' the spokesman said.

He said it was too early to know the cause of the crashes.

In the first crash, two men suffered minor injuries when a Chinook went down while hovering a few feet above the ground. Three others aboard were not hurt.

On Tuesday, a second Chinook crashed while in a low hover at the Mount Pleasant airfield on the Falkland Islands. Five of the eight men on board were slightly injured.

Last year, the U.S. Army grounded its 234 Chinooks for transmission checks after their manufacturer, Boeing, said certain transmissions were improperly assembled. Ten U.S. Army Chinooks have been involved in crashes since 1985.

The Royal Air Force also grounded its fleet in 1986 after a civilian version of the Chinook crashed in the North Sea, killing 45 people. A faulty gearbox was blamed.