France's national rail company SNCF is taking legal action after cyclists on a prominent race crossed train tracks seconds before a high-speed train whizzed past.
SNCF said the incident during the Paris-Roubaix race on Sunday in northern France was "irresponsible" and the cyclists could have been hit by the TGV train.
The International Cycling Union, or UCI, said it has requested a report into the "extremely worrying" incident which could lead to disciplinary action.
After some of the riders crossed the tracks 100 miles into the race, a railway crossing gate went down, nearly hitting one rider and forcing other cyclists to wait for the train to pass.
Some riders broke race rules by going around the gate barrier to cross the train track.
The legal action does not name anyone, but leaves it up to investigators to determine how it happened and who was responsible.
SNCF said it spends 30 million euro a year trying to reduce accidents at railway crossings.
The UCI's road race regulations say it is "strictly forbidden" to cross a train track when the barrier is down.
"Apart from risking the legal penalty for such an offence, offending riders shall be eliminated from the competition by the (race officials)," the governing body's rules state.
However, officials did not disqualify any riders, citing difficulties in identifying those at fault. Riders held up by the train were instead allowed to regain the positions they held before the incident. The race was won by John Degenkolb of Germany.