A massive 525ft rock pile has blocked the Bureya River leading to flooding and the evacuation of villagers from the remote area.
The Russian military’s first task is now to move all the debris that would reportedly fill 13,600 Olympic-sized swimming pools.
They along with scientists are also looking to discover what caused the mountain to collapse a month ago in the Khabarovsk region.
It has been been claimed that a UFO or a meteorite was behind the landslide.
A Russian defence ministry source revealed to the Siberian Times that a group of specialists have been sent to “conduct reconnaissance work” at the site.
“Given the significant size of the landslide, units of engineer and railway forces with special equipment as well as army and transport aviation will be involved in clearing the rock,” said the official.
A state of emergency has been called in the Verkhnebureysky and Bureysky districts due to the flood risk and makeshift housing has been put in place.
The river is also vital in providing water for the Bureyskaya hydro electric power reservoir.
Specialists are also rushing to a site, close to the village of Chekunda where the river level is rising fast, several centimetres each day.
Plenty of theories have been put forward for what took place and Professor Dave Petley, of Sheffield University, an expert in landslides, has played down the chances of their being any involvement from space.
He reportedly said: “The slope appears to show a pre-existing tension crack or depression that aligns with the rear of the failed mass.”
The fall left a new 160 metre high mound visible from space above the river bed.
People who first reached the site of the incident reported hot rocks which they could warm their hands on and a smell “like hydrogen sulphide”.
They thought the rock fall was caused by a meteorite similar to one which devastated Russia’s Chelyabinsk region 2013.
“I insist it was a meteorite,” said Alex Maslov, the district government chief of the remote part of the Khabarovsk region where the accident took place.
There were also reports of something a lot more mysterious going on.
Alexey Dyundin, 46, a local businessman, was driving through the neighbouring Yakutia region when he witnessed the event.
He said: “We saw a huge green-coloured body with a spectacularly bright and very long tail, falling almost vertically at about an 80 degrees angle.
“We saw it right in front of us, falling east to south. It all happened within three or four seconds.”