The snow and fog prevented aircraft from participating in the mission, while mountain patrols that left Thursday from the villages of Ocongate and Marcapata saw their progress hampered by deep snow.

“The conditions are very adverse. Snow in the area is now about 30 centimetres deep and fog makes it impossible to view the ground from the air,” said Cusco police chief General Hector Dulanto.

“We have not had positive results up to now, and clouds are starting to roll in,” Jeronimo Herrera, Marcapata police chief told AFP.

The helicopter left the city of Mazuco in the southeastern region of Madre de Dios late on Wednesday and set off across the Andes for the tourist hub of Cusco — but never showed up at its destination.

Officials held out hope that it could have made an emergency landing in the remote Hualla Hualla region, which is at an altitude of 4,725 metres, about 140 kilometres from Cusco.

On board the Sikorsky S-58 were eight South Koreans, a Czech, a Swede, a Dutch citizen and three Peruvians — two of them crew members — according to helicopter owner HeliCusco.

A police patrol helicopter flew Thursday over the area where the aircraft went missing but did not spot it, although the weather conditions again were very poor.

In Seoul, a foreign ministry statement confirmed that eight South Koreans were among the 14 people on board the helicopter.

It said they were engineers and officials from four South Korean companies returning to Cusco after conducting aerial surveillance on a possible site for a hydroelectric project near Puno in southern Peru.

“Attempts were made to reach them by mobile phones but calls were not answered. There were no automatic distress signals either, which should come from the helicopter if it crashes,” the ministry statement said.

A diplomat at the South Korean embassy in Peru told South Korea’s Yonhap news agency that the Peruvian air force picked up a GPS signal believed to be coming from the helicopter.

A search helicopter was dispatched to the coordinates but was unable to approach the site because of bad weather, the diplomat said.

Two officials from the South Korean embassy in Lima were in Cusco to monitor the search and rescue operations, Peruvian police said.

According to the US National Transportation Safety Board, there were seven helicopter accidents in Peru from 2007 to 2011, including three fatal. Three of the crashes were near Cuzco.

Helicopter experts say safety has steadily improved over the years worldwide, in part due to better technologies that help pilots cut through bad weather and dangerous terrain.

Human factors, such as complacency, remain the top reason for crashes.