The group of 54 cyclists included leaders Tadej Pogacar and Remco Evenepoel. The riders ignored a red light at a railway crossing, the most serious violation under the Belgian traffic code. The remaining 128 riders stopped when the barriers closed.
"Such offences pose serious risks to the safety of both riders and members of the public. That is why these offences are severely punished," the public prosecution office said.
"All the offenders have now been identified, and a report is currently being drawn up. We wish to emphasise that such offences, even in a sporting context, are unacceptable," the office continued.
Ignoring a red light at a railway crossing nearly always results in a fine. The fines range from €400 to €5,000.