Russian mainstream media frequently uses the term "bang" as a euphemism for a blast.
Baza, a Russian media outlet with security sources, said the blast on railway took place near the station of San-Donato, near an oil depot.
Last month, a Ukrainian source told Reuters that Ukraine's domestic spy agency had detonated explosives on a Russian railway line deep in Siberia, the second attack in a week on military supply routes in the area.
The Russian news agencies said on Monday no one was injured and there was no damage from the latest incident.
RBC, citing the Russian Railways, said traffic in the area was "restricted", and some trains might run behind schedule.
(Reporting by Reuters; editing by Barbara Lewis)
