(CNN) -- At least three people died after their helicopter crashed late Monday in western Norway, authorities said.
Norwegian police spokesman Gry Benedicte Halseth said in a statement that the number of people on board has not been established. But Gudmund Taraldsen, an officer with the Norwegian Civil Aviation Authority, told CNN that there were five people total on the helicopter when it went down, meaning two people are still unaccounted for.
The helicopter was hired by house builders to fly up into the Norwegian mountains, Halseth said. The aircraft -- an Aerospatiale 350 -- crashed before 8 p.m. Monday in a remote locale at the bottom of the Hardanger fjord, east of Bergen, Taraldsen said.
"I don't have any information about the cause of the accident, but there are very poor weather conditions at the site," the aviation authority officer said.
Another group, who had flown into the area before, reported the crash. They have been flown out of the area and are being taken care of by a local crisis team, according to Halseth.
The crash site has been cordoned off and will be under surveillance overnight, the police spokesman added. Authorities have established a no-fly zone around the locale.
Early Tuesday morning, federal crash site investigators and officers with the Norwegian police are expected to arrive on scene to start their investigation.
"This is the worst helicopter accident we have ever had over land," Taraldsen said.