Debris found Saturday in northern Sweden came from a Norwegian Hercules military aircraft with five crew that disappeared earlier this week, Norwegian Defence Minister Espen Barth Eide said, according to dpa. "We know that there has been a serious plane crash," Eide told an Oslo news conference, noting that debris had been spread over a large area. The plane had hit the western part of the Kebnekaise massif, which forms Sweden's highest mountain, he said. A search was ongoing for possible survivors, but there was no information about the crew of four men and a woman, he said. "A very grim picture has emerged," said General Harald Sunde, head of the Norwegian defence forces. The C-130 J Hercules plane went missing Thursday after taking off from Evenes airport in northern Norway, bound for Kiruna in northern Sweden. Search efforts have been hampered by poor weather but conditions improved early Saturday. The winds had dropped but it continued to snow. Four avalanches were reported overnight in the search area, adding to the challenges facing the rescue workers. Helicopters and other aircraft were also deployed in the search. All-terrain carriers and snowmobiles were used as there are no roads in the area. The plane was taking part in the Cold Response military exercise hosted by Norway. Forces from Britain, Canada, France, the Netherlands, Sweden and the United States were among the participants. The weather in the area was poor when the plane disappeared from the radar shortly before 1400 GMT on Thursday, about 80 kilometres west of Kiruna.