The collision occurred around 6:30 a.m. near Hiller, about 40 kilometers (25 miles) north of Copenhagen. Roughly a dozen other people have minor injuries, according to the Greater Copenhagen Fire Department.

Everyone has been evacuated out of the trains, according to a spokesperson for the North Zealand police.

Officials originally said four people were critically injured but revised that figure hours after the crash. It was not immediately clear whether the train's drivers were among the victims.

Investigators are looking into what caused the collision. Photos from the scene show the front ends of the trains smashed, though both remained upright on the tracks.

The mayor of the nearby town of Gribskov, Trine Egetved, in a post on Facebook, said some of the injured were flown to the hospital.