GAUHATI, India >> Police and rescue teams from India and Bhutan searched their mountainous border Sunday for a helicopter that vanished while transporting the chief minister of the northeastern Indian state of Arunachal Pradesh.

The single-engine helicopter was carrying Chief Minister Dorjee Khandu, two other passengers and two pilots when it disappeared in bad weather Saturday just 20 minutes after taking off from the Himalayan Buddhist retreat of Tawang for the state capital, Itanagar.

“We are still hoping, but we are extremely worried because it has been a long time now since the helicopter disappeared over treacherous terrain in the high Himalayas,” Khandu’s aide Kiren Rijiju said. Temperatures overnight in the area were below freezing.

About 2,400 Indian army troops fanned out Sunday to search the forests along the border, while two Indian air force fighter planes often used in mapping also searched from the air before air operations were called off at dark Sunday.

The aerial search is to resume Monday, and officials hope the weather will be clear enough for air force helicopters to join the effort.

Beginning at dawn Sunday in eastern Bhutan, “police along with local villagers have set out to locate the helicopter at mountain tops and grazing grounds,” while Buddhist monks were praying for divine intervention to help in locating the missing aircraft, said the country’s Tashiyangtse district deputy commissioner Sangay Duba.

The Indian Space Research Operation has assigned a satellite to take pictures over the Sella Pass area that might reveal the helicopter’s location.

Prime Minister Manmohan Singh sent two government ministers to supervise the search from Itanagar.

Khandu, 56, is a former army intelligence official elected in 2007 as Arunachal Pradesh’s top official.

There have been two helicopter crashes in the area in the past two weeks.

On April 19, an aircraft operated by Indian state helicopter company Pawan Hans — which was also handling the chief minister’s aircraft on Saturday — crashed in the mountains of Tawang, killing 17 people on board.

Three days later, an army helicopter went down in the neighboring state of Sikkim, killing four.

Pawan Hans has suspended all services.