OSLO, Norway — A Norwegian military transport plane with five people aboard went missing Thursday during an exercise and was feared to have crashed in bad weather in a mountainous area in northern Sweden, officials said.

The C-130 was heading from Evenes, on Norway's Arctic coast, to the Swedish city of Kiruna when it disappeared from radar screens just before 3 p.m. (1400 GMT), rescue coordinators said.

"We have to assume that we are looking for a plane that has crashed," Norwegian military spokesman John Espen Lien told The Associated Press.

A military helicopter searching the area picked up an emergency signal near mount Kebnekaise, 80 kilometers (50 miles) west of Kiruna, Swedish air rescue spokesman Jonas Sundin told AP.

"They thought they heard a weak signal," he said, adding rescuers were trying to pinpoint the location of the signal, but were hampered by poor visibility because of cloud cover and strong winds whipping up snow. By late Thursday there was still no sign of the plane.

The four men and one woman on board were Norwegians, officials said. The Norwegian Armed Forces identified them as Staale Garber, Truls Oerpen, Bjoern Yngvar Haug, Steinar Utne and Siw Robertsen.

Rescue services from Sweden and Norway, as well as aircraft taking part in the exercise, including a U.S. AWACS surveillance plane, were involved in the search, Swedish rescue officials said. Soldiers also entered the area on foot.

Search and rescue coordinator Birgitta Eckermark told AP that the crew's last contact with the Kiruna control tower was at 2:43 p.m. (1343 GMT) and the plane dropped off radar 13 minutes later.

The plane went missing while on route to Kiruna to pick up personnel during a winter exercise called Cold Response, with 16,000 soldiers from 14 countries taking part.

The purpose of the Norwegian-led exercise "is to rehearse high intensity operations in winter conditions within NATO with a U.N. mandate," the country's military said.

Ritter reported from Stockholm.