LONDON - Five people were killed when their helicopter crashed in poor conditions in a mountainous part of Wales, rescuers said Thursday after a major search operation. 

Authorities found the wreckage of the privately-owned Twin Squirrel chopper in Snowdonia, a national park in northwest Wales, after it went down en route to Dublin. 

The bodies are being recovered from what local police said was “very difficult and challenging terrain”. 

“Local conditions were described as atrocious, with visibility down to less than 10 metres (33 feet) in places,” said Gareth Evans from the North Wales Police force. 

“The terrain where the aircraft has been located is remote and, in places, hazardous.” 

He said details of those on board would not be revealed until their bodies had been formally identified, and specialist family liaison officers were supporting the relatives. 

Evans said a full investigation had been launched and urged people to stay away from visiting the area, a popular tourist spot, in order to facilitate the probe. 

The Twin Squirrel is a widely used twin-engine light utility helicopter with a reputation for durability and low maintenance. 

First introduced in the mid-1970s, the all-weather aircraft is used for both civil and military purposes. 

It has a cruising speed of 140 miles (225 kilometres) per hour and a range of nearly 440 miles.