There are fears a plane carrying Australian tourists has crashed near the Kokoda Track in Papua New Guinea.
Helicopters are searching the Owen Stanley Range for the missing Airlines PNG charter plane, which left Port Moresby with 11 passengers and two crew on board.
Australia's Department of Foreign Affairs and Trade says nine of the passengers on are known to be Australians.
The ABC reports the passengers on Flight CG4684 were travelling as part of a tour group organised by No Roads Expeditions and were due to walk the Kokoda Track.
A search is under way in the mountainous terrain near Mt Kokoda using at least two helicopters, but bad weather and poor visibility are hampering efforts on Tuesday.
Australian Foreign Affairs Minister Stephen Smith says consular officials in Port Moresby are doing everything they can to help. Authorities are also checking nearby airfields for the plane.
Airlines PNG says the last communication received from the missing twin otter plane was as it approached Kokoda. The airline says the plane has an emergency locator beacon but it has not received any signals from it.
At least 19 planes have crashed since 2000 in Papua New, killing 16 people, including three Australians and three New Zealanders.
The Kokoda Track is popular with tourists, as it was where Australian forces halted a Japanese troop advance on Port Moresby during World War II.