Apparently deliberately set blazes to clusters of electrical cables have caused cascading cancellations on the Paris train network, all but shutting down services at one of the French capital's busiest stations.
Two fires damaged 48 cables, Transport Minister Clement Beaune said, describing it as "an act that is scandalous".
Rail operator SNCF said the cables powered signals for trains on the network.
It filed a legal complaint, calling the overnight damage deliberate.
The motives for the apparent vandalism were unknown.
But it largely shut down Gare de l'Est, a station that generally links Paris to cities and towns in the east, including in neighbouring countries.
SNCF said the circulation of high-speed trains and slower regional trains to and from the station was suspended, with only services on three lines spared.
SNCF said repair crews were working to restore the affected lines.
But it also warned that services at the station, which is used daily by hundreds of thousands of passengers, could be suspended throughout Tuesday.