Two commuter trains collided head-on near the Danish capital on Thursday injuring 17, of whom five were in critical condition, emergency services said.
"We can't provide any details for now about the cause of the accident," police official Morten Kaare Pedersen told reporters.
He said police were alerted to the accident at 6:29 am (0429 GMT), which occurred about 40 kilometers (25 miles) north of Copenhagen between the towns of Hillerod and Kagerup.
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.
She said the crash occurred on a local rail line that's used by many Gribskov residents, employees and schoolchildren.
