Indonesian special forces have found the voice-and-data recorder of a new Russian passenger jet that crashed into the slopes of an Indonesian volcano with 45 people aboard.

The "black box" could help explain the cause of the deadly crash of the Sukhoi Superjet 100, which had been on a short demonstration flight for potential buyers. 

Search and rescue agency spokesman Gagah Prakoso said on Wednesday it was found near the tail of the shattered wreck at the bottom of a 500 metre ravine.

The device, which was was badly burned and lost its orange colour, was delivered to investigators late on Tuesday.

Tatang Kurniadi, who heads the National Commission on Safety Commission, said he and his Russian colleagues would make a joint official announcement about the black box later on Wednesday.

He said data retrieved from the device would be analysed in Indonesia, with assistance from Russian experts.

The Superjet 100, Russia's first passenger jet model since the fall of the Soviet Union two decades ago, was being demonstrated for potential buyers when it crashed into Mount Salak at 800kph on May 9.

Source: Agencies