The collision between the bus and a train happened near the city of Vladimir, east of Moscow.
At least 19 people were killed on Friday when a train slammed into a bus that had broken down at a level crossing in Vladimir near Moscow, Russia's investigative committee said in a statement.
The bus, which was carrying migrant workers from Uzbekistan, was shunted several hundred metres down the track, Russia's Rossiya 24 TV channel reported.
Footage showed fragments of what was left of the bus strewn across the track. The train itself appeared to have sustained no visible damage.
"The bus stalled on the track," Vladimir Myagkov, a spokesman for Russian Railways, told Rossiya 24 at the crash site.
"Some people say the passengers tried to push the bus off the track. At that moment the train approached and a collision occurred," he said.
Though carrying workers from the Central Asian nation of Uzbekistan, the bus had a license plate registered in Kazakhstan, Russian news agencies reported.