Dozens of Russian experts combed a remote mountainside in Indonesia Sunday searching for the flight recorders of a Sukhoi jet that slammed into a dormant volcano killing everyone on board.

As more body bags containing victims of Wednesday's crash arrived in Jakarta, transport ministry spokesman Bambang Ervan said a team of 41 Russians plus several hundred Indonesians were searching the site.

“They are now working at the crash site to collect all information and evidence on the ground,” Ervan told AFP.

He said Indonesian investigators had questioned staff at the control tower for information about the Russian plane's last contact with the ground and radar readings before it slammed into Mount Salak, a dormant volcano.

“We haven't found the black boxes,” said Daryatmo, head of the national search and rescue agency, who goes by one name.

Reaching the site, just 80 kilometres south of Jakarta, and retrieving scattered body parts and debris in jungle terrain on the near-vertical mountain has posed an extreme challenge for rescuers.

Indonesian marines and professional climbers were Sunday attempting to descend into a deep ravine, Daryatmo said.

“We will reach 100 metres further below. Hopefully we will find (the black boxes, or flight data recorders) there,” he said.

Authorities said more Russians were trekking to the site and that a total of 73 Russians would take part in the operation.

The Sukhoi Superjet 100 disappeared off radars during what was supposed to be a short demonstration flight to tout Russia's first post-Soviet civilian aircraft.

Officials have confirmed that there were no survivors on the plane carrying at least 45 people, mostly Indonesian airline representatives and eight Russians.

Nearly 20 body bags with the remains of victims had arrived in Jakarta by Sunday for forensics tests and identification, authorities said.

“The location today is very steep, so it's not going to be easy to carry the body bags from down there and up (to the helipad),” Daryatmo said.

Questions are swirling over why the plane crashed with an experienced pilot at the helm.

A Russian fact-finding committee has said there were indications that safety standards were violated.

Key to the mystery is why the pilot requested permission to descend from 3 000 metres to 6 000 feet before the plane disappeared from radar screens and slammed into Mount Salak, which rises to 7 200 feet. - Sapa-AFP