Shale's math problem

Two trains have collided in southern Poland, leaving 16 people dead and 58 hurt, local officials say.

The accident occurred on Saturday evening on the Warsaw-Krakow mainline at the small town of Szczekociny, according to Polish TV.

Two express trains, one of which was on the wrong track, collided head-on, a senior railway official said.

Prime Minister Donald Tusk called the accident Poland's "most tragic train catastrophe... in many years".

Mr Tusk arrived at the scene early on Sunday morning, with three other cabinet ministers.

President Bronislaw Komorowski has said he will announce a period of national mourning once emergency teams have completed their work to remove the wreckage from the track.

"The scope of this disaster is sufficiently large to warrant national mourning," he said.

The two trains, comprising 10 carriages in total, were carrying an estimated 350 passengers at the time of the crash.
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Helicopter ambulances from Warsaw and Wroclaw helped to take the injured to hospitals.

"The rescue is difficult and complicated," firefighter Jaroslaw Wojtasik told Polish television.

"The damage to the wagons is huge. We have contact with victims. We are approaching very cautiously."
Engineering works

Prosecutors have said that they have identified six of the 16 people killed in the train crash in Szczekociny, one of whom was an American woman.

Among those injured, six were Ukrainians and one was from Moldava, officials said.

The accident occurred at 21:15 (20:15 GMT), when a train travelling north from Przemysl to Warsaw collided with a southbound train from Warsaw to Krakow.
Rescuers work at the scene of a train crash in Szczekociny near Zawiercie (Silesia) in Poland Coaches were destroyed "like a concertina", an eyewitness said

Scheduled engineering works were taking place on one track at Szczekociny station at the time of the accident.

The Krakow train was on the wrong track, Andrzej Pawlowski, a member of the board of the state railway company PKP, told the TV station TVN24.

Three coaches are reported to be especially damaged, and the rescue operation is focusing on finding passengers there.

The three coaches were "completely destroyed - like a concertina", one eyewitness told the Gazeta Wyborcza newspaper.

Another passenger estimated that his train was travelling about 120km/h (75 mph), when it started braking very sharply.

"Then we felt a powerful impact, and we were thrown about the compartment," the passenger told TVN24.