MOUNT SALAK: Search teams who scaled a volcano's steep slopes found at least 12 bodies Friday near the wreckage of a Russian-made jetliner that crashed in Indonesia during a demonstration flight for potential buyers, an official said.

All passengers aboard the Sukhoi Superjet-100 that crashed Wednesday are feared dead.

"Today we have discovered 12 victims, all dead," Rear Marshal Daryatmo, head of the national search and rescue agency, told reporters Friday.

Many of the bodies found Friday had been torn apart in the crash, said Lt. Col. Oni Juniato of the Indonesian marines, whose search team found eight corpses before returning to base camp further down the mountain.

"We see many other victims ... but the ravines and steep cliffs prevent us from reaching them," Junianto said

Local television showed what appeared to be the plane's tail with the blue-and-white Sukhoi logo, part of a wing and bits of twisted metal scattered along the slope like confetti.

About 85 soldiers, police and volunteers used ropes to climb up to the wreckage through jungle on the near-vertical slopes of Mount Salak, search and rescue agency spokesman Gagah Prakoso said by telephone.

Thick fog and the mountain's jagged slopes kept helicopters from landing at the crash site, so the bodies remained there along with the search teams.

The soldiers, police and volunteers fashioned a landing area by hacking down trees, but Prakoso said the helicopters were recalled to Jakarta late Friday because the fog limited visibility to only about 5 meters (15 feet).

The jetliner slammed into the dormant volcano at nearly 800 kph (480 mph) during drizzle. Russian and French investigators have joined the investigation into the cause.

The Superjet-100 is Russia's first new model of passenger jet since the fall of the Soviet Union two decades ago and was intended to help resurrect its aerospace industry.

The ill-fated Superjet was carrying representatives from local airlines and journalists on what was supposed to be a 50-minute demonstration flight. Just 21 minutes after takeoff from a Jakarta airfield, the Russian pilot and co-pilot asked for permission to drop from 10,000 feet to 6,000 feet (3,000 meters to 1,800 meters). They gave no explanation, disappearing from the radar immediately afterward.

It was not clear why the crew asked to shift course, especially since they were so close to the 7,000-foot (2,200-meter) volcano, or whether they got an OK, officials have said.

Communication tapes will be reviewed as part of the investigation, but it's unlikely they will be released to the public any time soon.