Indonesian special forces and professional climbers scaled down a treacherous ravine on a volcano face Sunday in search of the missing flight recorder that could explain the deadly crash of a Russian-made jetliner.

The Sukhoi Superjet-100 had 45 people aboard when it crashed into Mount Salak on Wednesday during a flight intended to woo potential Indonesian airline buyers.

All aboard are presumed dead, and helicopters have been ferrying the victims' remains to Jakarta, the capital, for identification since Saturday.

It's unclear what caused the crash about halfway through a planned 50-minute flight, so finding the "black box" recorder is a priority.

Dozens of Indonesian and Russian investigators were searching Sunday in a ravine near where the plane's scattered wreckage was found on the slopes of the long-dormant volcano, 80 kilometers (50 miles) southwest of Jakarta, top civil aviation official Herry Bakti Gumay said.

Local news station TVOne reported that search teams had spotted a device that might be the black box lodged in a tree near the bottom of the 500-meter-deep (1,500-foot-deep) ravine and were trying to reach it.

However, the recorder had not been reached by the time the search was called off for the day Sunday, said Tatang Kurniadi, who heads the National Transportation Safety Commission.

A landslide was triggered when the Superjet slammed into the side of the mountain, and much of the wreckage including the engine and landing gear were covered in rocks and dirt, TVOne reported.

The Superjet is Russia's first new model of passenger jet since the fall of the Soviet Union two decades ago.

Wednesday's ill-fated flight was a demonstration for Indonesian fast-expanding domestic airlines that the manufacturer hoped would buy the jet.

Indonesia has added 36 new passenger and cargo airlines in the past five years and seen growth of 15 to 20 percent in the sector as companies rush to serve an emerging middle class amid the island nation's economic boom.