BBC correspondent John Andrew: Every part of the wreckage is being examined

Paramedics Tony Richardson, 47, and Mark Darby, 37, and pilot Captain Graham Budden, 40, died instantly when the helicopter collided with power lines and plunged into a field in Buham near Rochester airport.

The ambulance is understood to have just taken off from Rochester Airport to attend a road accident but it was called off after it was discovered the crew was not needed at the crash.

The helicopter burst into flames on impact, killing all three men.

The chief executive of the Kent Air Ambulance Trust, Kate Chivers, broke down in tears as she paid tribute to the three men.

She said: "I have always believed the crews are very special. They do a very difficult job in difficult circumstances."

She said the death's of the three men was "Kent's loss".

Mrs Chivers said the service had been left "totally devastated" by their deaths.

Some of the crew's colleagues are being counselled because they are so upset.

Mr Darby had joined the ambulance service in 1989 and had flown with the air ambulance since 1994.

The BBC's Ishbel Matheson reports from the scene

Mr Richardson had joined in 1982 and had flown with the air ambulance since 1996.

Mr Budden, who was married with two children, was an RAF pilot for five years,before joining Medical Aviation Services which operated the helicopter.

He had served in the Falklands, flying Sea King helicopters

He had announced he was to give up flying helicopters just days before his death to work for an airline.

Chivers: the trust is "totally devastated"

The helicopter was not supposed to have been on duty - the crew had been attending a charity event earlier in the afternoon.

The paramedics were taken from Kent's ambulance crew and work for three-week periods every two months.

The service has been running for 10 years and has attended around 9,000 incidents.

The accident caused damage to the electricity pylons, resulting in a 50-minute black-out in the area around the airport.

The Twin Squirrel helicopter was purpose-built as an ambulance and run by the Kent Air Ambulance Trust.

It was funded by public donations and a local lottery and had been used by the ambulance service for two years. It was previously used by the police.