A Thai helicopter has lost contact with ground control during a search and rescue effort for two missing mountaineers on Southeast Asia`s highest peak, officials said Sunday.
The helicopter, part of a search team led by a controversial Myanmar tycoon, was carrying three people, including a Thai pilot, expedition organisers said.
"The chopper... lost contact (Saturday) while on their way to drop supplies to rescue teams searching for the two missing mountaineers," the Htoo Foundation, which deployed the helicopter, said in a statement.
Contact was lost with ground control shortly after it took off from Putao airport in northern Kachin state on Saturday afternoon, it added.
Two other helicopters from the foundation and a government Mi-17 helicopter are also searching for the missing aircraft "and soldiers, local police force and local people are cooperating", the statement said.
The missing mountaineers, Aung Myint Myat and Wai Yan Min Thu lost contact with the rest of their team in early September after reaching the summit of Hkaka Borazi in Myanmar`s portion of the Himalayas.
The mountain, in the northern state of Kachin, is 5,881 metres (19,295 feet) high.
According to Thailand`s Advance Aviation, the missing helicopter was fitted with an Emergency Location Transmitter (ELT) which sends an alert in case of an accident.
"Since the plane lost contact, we have not received any alert so we believe it was not an impact landing," Punyisa Chaisong, a sale manager of Advance Aviation, told AFP.
She added that poor weather conditions had made it difficult to contact the team in the helicopter.
Myanmar`s Htoo Foundation is the charitable arm of the sprawling Htoo Group of Companies, with interests from agriculture to an airline, run by businessman Tay Za.
The tycoon, who has links to the former ruling junta and is blacklisted by US sanctions, left Yangon to launch a rescue mission to the mountain, which is in an area where he narrowly survived a helicopter crash a few years ago.
Tay Za`s empire spans teak logs to an airline -- although he has also been accused of arms dealing -- and he is an enthusiastic mountaineer.
The Htoo Foundation said bad weather had hampered earlier attempts to search for the men.