The aircraft disappeared early on Saturday in Taplejung district, about 500km east of Nepal's capital Kathmandu.

A Nepalese Cabinet minister, a Finnish diplomat and aid workers and journalists were among those on board the helicopter chartered by the conservation group the World Wildlife Fund.

Also on board was Australian conservationist Dr Jill Bowling - the London-based director of the World Wildlife Fund UK. Her brother in Darwin, Mark Bowling, said they were just waiting and hoping for the best. Dr Ray Nias, from WWF Australia in Sydney, said that Dr Bowling's colleagues have been shocked by the news but they are hoping everything is well.

Anil Manandhar is the Director of the WWF Conservation Program in Nepal.

"We still don't believe that the worst has happened, we still have hope."

Poor weather forced rescue teams to return to nearby airports and security camps early on Sunday. Search operations are due to resume as soon as the weather improves in the thickly forested, mountainous region. Officials say the helicopter was carrying Nepal's Forestry Minister Gopal Rai, Charges D'Affaires of the Finnish Embassy Pauli Mustonen and Deputy Director of USAID in Nepal Margaret Alexander. Other WWF staff were also among those missing, including four Nepalis, a Canadian and an American.