A spokesman for Sloane Aircraft in Northamptonshire - where tests on the wrecked �2.5m helicopter have been conducted - said mechanical failure had been ruled out.

The force helicopter before the accident

It is expected that a report into the incident - due out later this week - will indicate that human error was to blame.

The eight-seat Augusta 109 Power came down near a dual carriageway at Cross Hands, injuring two of its crew.

Dyfed-Powys Police is set to buy in air cover from other police forces, while its helicopter remains out of action.

It is feared the helicopter could be a total write-off.

Initially, it was believed that the aircraft developed mechanical problems as the crew returned to the force's headquarters in Carmarthen.

It had been taking a patient to Morriston Hospital in Swansea, on Tuesday and was on its way back to the force headquarters when it had to land near a scrap yard in Cross Hands, Carmarthenshire.

The civilian pilot and one of the two police officers on board were released after treatment at the West Wales General Hospital at Carmarthen.

The second officer was unharmed.

The helicopter's rotor blade was badly damaged

Bad weather is not thought to have been a factor in the emergency landing.

The incident has been reported to the Civil Aviation Authority and an inquiry is expected to be carried out by the Air Accident Investigation Board.

This latest accident follows an incident in April 2000 when the South Wales Police helicopter crashed into the roof of a Cardiff house while pursuing a stolen car.

A report by the Air Accident Investigation Branch revealed that a badly fitted part caused that mechanical failure.