The reindeer died at the “Dead Road” – one of the world’s most remote railways.
However, it is not clear why they did not leave the track when they saw the train coming – or when it began to knock down other animals.
Police are now investigating the animals’ gruesome death, Siberian Times reports.
Photos from the scene show the bodies of the deer strewn either side of the track where they were knocked out of the way by the train.
The snow is stained red with deer blood, while painful injuries are visible on the animal corpses.
These are generally consistent with having been hit by a train.
However, sceptics are asking how a train could have killed 70 deer in one go, with none of them running away.
They have asked why generally timid animals like reindeer would have remained on the track when the train approached, and not scattered long before it got close to them.
Others have asked why the driver did not break to avoid the reindeer – though it can take over 1km for a train to come to a stop after the brakes are applied.
The “Dead Road” where the reindeer died is among the most remote transport routes in the world.
It was built by Gulag prisoners under Soviet dictator Josef Stalin.
The bleak train line transports passengers and goods across Siberia.