At least one person was killed and dozens injured after a passenger train rammed into a maintenance crane on the tracks in the Netherlands early on Tuesday, emergency services said.
The train, carrying at least 50 people, derailed after it hit construction equipment in Voorschoten, a village near The Hague at about 3.25am.
The crane operator was killed and many of the passengers were seriously injured.
Some of the injured were treated on the spot and 19 were taken to hospital.
The maintenance work was planned and standard, but "we have no idea how the crane got on the track which was still open for traffic", said John Voppen, chief executive of infrastructure company ProRail.
"The crane was part of maintenance work on two tracks which were closed for traffic, while two other of the total of four tracks remained open for train traffic."
Police opened an investigation to establish if any crime had been committed. Another independent probe was opened into the cause of the crash.
Mr Voppen called the accident "a black day for Dutch railways".
The front carriage of the night train from Leiden to The Hague derailed and ploughed into a field, ANP news agency reported.
The second carriage was left on its side and a fire broke out in the rear carriage but was later extinguished, ANP said.
Video footage from inside the train showed chaotic scenes as passengers tried to get out of the wreckage in darkness.
The driver of the passenger train is in hospital with broken bones, NS (Dutch Railways) chief executive Wouter Koolmees said.
Prime Minister Mark Rutte and the Dutch royal family were among those who expressed their sympathy for the victims.
"My thoughts are with the relatives and with all the victims. I wish them all the best," Mr Rutte said in a tweet.
"We deeply sympathise with all of them," King Willem-Alexander and Queen Maxima said.
Voorschoten mayor Nadine Stemerdink said it was "an incredibly tragic accident".
"I sympathise with the victims. Unfortunately, there is also a fatality to mourn. My thoughts go out to all the family and friends of those involved," she added.
Trains between Leiden and parts of The Hague were cancelled, NS said on Twitter.
