THE HAGUE (AFP) ― Two trains collided head-on just outside Amsterdam on Saturday, injuring at least 60 people, up to 20 of them seriously, Dutch transport police said.

“There are 60 people injured ― some 15 to 20 badly,” police spokesman Ed Kraszewski told AFP, after the crash near Sloterdijk in the western suburbs of Amsterdam, but he added “I can’t give exact figures.”

A spokeswoman for the Dutch capital’s fire service put the number of seriously injured at 56, adding “tens of others were slightly wounded.”

The accident happened at around 6.30 p.m. when a local train leaving Amsterdam hit a high-speed train, Dutch rail network Prorail spokeswoman Babet Verstappen told AFP.

But both trains were travelling relatively slowly at the time, Dutch NOS television reported: each moving at around 50 kilometers-an-hour.

One had just left Amsterdam central station; the other Amsterdam Sloterdijk.

Witnesses quoted by the Dutch media television said the impact had not been violent.

Emergency personnel treated some of the wounded at the scene, on a bridge between Sloterdijk and Amsterdam Central Station, Verstappen added.

The worst injured were taken to hospitals, while less seriously hurt passengers were booked into hotels in the city, she added.

Many of the injured suffered from broken bones and bruising, Dutch news agency ANP reported.

It cited witnesses who described how travelers had been thrown about inside the carriages or up against their windows, some of which had shattered.

Witnesses said they heard a long hoot from one of the trains before the crash.

Passengers on the social network Twitter said they were “smashed against the trains’ frames” or “thrown from their seats,” ANP added.

Pictures from the scene showed the crushed front ends of both the trains and smashed windows in some of the carriages.

“Some of the injured had to be rescued from inside the train,” added Amsterdam fire service spokeswoman Elke van den Hout.

By late Saturday evening, all the injured had been rescued from the trains, which remained on the tracks, railway police spokesman Kraszewski said.

The cause of the accident remained unknown, but police have launched an investigation, he added. The crash has shut down rail traffic in the west of the city, including Amsterdam Central station and the service to Schiphol airport, Prorail’s Verstappen said.

Bus services were being laid on to try to get passengers to their destinations.

The Netherlands’ worst train disaster happened on January 8, 1962, when two passenger trains smashed into one another at Harmelen, near the central Dutch city of Utrecht, killing 93 and injuring 52 others.

Earlier this year, a monument was unveiled to mark the 50-year anniversary of the accident which happened in thick fog when a train driver missed a warning signal and the two trains also crashed head-on.