Indonesian officials say a helicopter has spotted what is thought to be wreckage of the Russian Sukhoi Superjet plane that disappeared on Wednesday.
The Sukhoi Superjet 100 vanished from radar screens 50 minutes after taking off from Jakarta for a brief demonstration flight.
Officials said the helicopter had seen debris on the side of a cliff near a dormant volcano.
About 50 people are said to have been on board the aircraft.
There was no information given about the fate of those on the plane, but a search and rescue operation is continuing in the area.
"The aeroplane crashed at the edge of Salak mountain," Indonesian President Susilo Bambang Yudhyono said on television.
"I have spoken directly to our officer in the field, it was found around 1.5km (one mile) from the spot where the plane last made contact," he said.
"An investigation must be carried out immediately and thoroughly. Search and rescue operations must prioritise finding any survivors."
Eight Russian pilots and technicians, Indonesian airline representatives and journalists were among those said to be on board the plane.
Aerial searches for the plane on Wednesday were hampered by darkness and strong winds. Fog early on Thursday also delayed search efforts.
The plane took off from east Jakarta's Halim Perdanakusuma airport at 14:00 (07:00 GMT) on Wednesday, on its second flight of the day.
At 14:50, it was recorded as dropping from 10,000ft (3,000m) to 6,000ft near Salak, a peak measuring 7,200ft (2,200m).
Juanda, a villager who lives near the mountain, told local TV: "I saw a big plane passing just over my house."
Rescue teams on the ground were working to reach the site where the debris was spotted, officials said.
Sukhoi officials have been on an Asia-wide tour in recent months to show off their aircraft to airline firms.
The Superjet, a mid-range airliner that can carry up to 100 people, is military plane-maker Sukhoi's first commercial aviation plane.
It was created by a joint venture, majority-owned by Sukhoi, with Italy's Finmeccanica and a number of other foreign and Russian firms also involved.
Sukhoi aimed to sell 42 of its planes to Indonesia, which has witnessed a fast-expanding aviation market to cater for a growing middle class in the world's fourth most populous nation, Reuters adds.