In a separate incident, Alpecin-Deceuninck rider Van der Poel was struck by a water bottle while also in the lead alone at Paris-Roubaix on Sunday, before going on to win the race for a record-equalling third time in a row.
A man handed himself in to a West Flanders police station on Monday and the public prosecutor is deciding what action to take.
Van der Poel, 30, has been involved in several incidents involving spectators in recent years.
In December 2023, he spat at some spectators during a cyclocross race in the Netherlands, saying he had had enough of being booed and having liquid thrown at him.
The following April, he had beer thrown at him during the Tour of Flanders.
