COPENHAGEN, Denmark (AP) — Norwegian officials say four people from Sweden and Finland are missing after an avalanche in northern Norway but strong winds, heavy snowfall and poor visibility are hampering rescue efforts.

A woman from Sweden and three men from Finland were last heard from on Wednesday afternoon. A search-and-rescue operation was launched after a 300-meter (990-foot) wide avalanche was reported in the Tamok valley, near the northern city of Tromsoe, where the party had gone skiing.

Police spokesman Morten Pettersen says "there was little chance to get a helicopter into the area." He told a news conference Thursday in Tromsoe that "we cannot take that risk."

Baard Rannestad of the University Hospital of North Norway told reporters at the news conference that the skiers' "chances to survive diminish with every passing minute."