South Jutland Police and the Danish Road Directorate (Vejdirektoratet) confirmed that a van had been hit by a rock thrown from a bridge.
Police later confirmed via press statement that no injuries had been sustained as a result of the vandalism, although the windscreen of the van that was hit by the rock was smashed.
The stone was thrown from a bridge at exit 68 of the E45 motorway near Vojens. Police were informed of the incident at 11:21am, according to the statement.
Drivers who may have passed the bridge around the time of the incident are encouraged to contact the police should they have any information that could lead to the three individuals.
Police currently have no firm leads as to their identity, according to the statement.
The motorway was temporarily closed as police secured potential evidence and was reopened at around 2:30pm.
A similar incident is currently being investigated by police on the island of Funen, reports news agency Ritzau.
In the early hours of September 9th, a rock weighing 40 kilograms was thrown from a motorway bridge at the Spedsbjergvej road, according to the report.
A passing car was able to avoid the rock in that incident, which is being treated by police as an attempt to kill one or more motorists.
Last year, a German woman was killed after a stone thrown from a bridge hit her car, also on the Funen motorway.
The woman's husband survived his injuries and the pair's child was unharmed.
Neither of the two Funen cases have been resolved, reports Ritzau.