Two trains running on the same track collided head-on in southern Poland late Saturday, leaving 15 people dead and 56 injured _ the country's worst train disaster in more than 20 years.
President Bronislaw Komorowski on Sunday said when rescue efforts are over he would make an announcement about a period of national mourning due to the scope of the suffering involved.
Several of the passengers were foreigners, including people from Ukraine, Spain and France, but none of them were among the dead or mostly seriously injured, Prime Minister Donald Tusk said.
"This is our most tragic train disaster in many, many years," Tusk said.
An unnamed passenger interviewed on the all-news station TVN24 said he felt the force of the collision.
"I hit the person in front of me. The lights went out. Everything flew," he said. "We flew over the compartment like bags. We could hear screams. We prayed."
Rescue workers were bringing in heavy equipment Sunday to try and free a body from the mangled wreckage of the train, while the injured are being treated in several area hospitals. A doctor in one, Szymon Nowak, said many of the injured were in a serious condition, with some in artificially induced comas.
"It's a very, very sad day and night in the history of Polish railways and for all of us," Tusk said.
The accident in the southern town of Szczekociny comes less than three months before millions of football fans will start crisscrossing the country _ many by train _ to watch matches at the Euro 2012 football championships, which is being co-hosted by Ukraine.
Poland, which is still recovering economically from decades of communist rule, doesn't yet have the high-speed trains of Western Europe. Many of the local trains are old and run slowly. However, the country does offer fairly speedy service between some key cities, and trains are generally seen as safe and used by many in the country of 38 million.
Prosecutors have opened an investigation into how one of the trains ended up on the wrong track, but officials said it was too soon to draw any conclusions.
One train was traveling from the eastern city of Przemysl to Warsaw in the north, while the other _ on the wrong track _ was heading south from Warsaw to Krakow. Maintenance work was being done on the tracks before the accident happened, officials said.
President Komorowski visited the crash site Sunday, as well as hospitals where the injured were being treated.
"The scale of this phenomenon is so large that there should be nationwide mourning," he said.
The tragedy was the worst involving trains since 1990, when 16 people were killed in a collision involving two trains in the Warsaw suburb of Ursus. Since then, the most serious Polish rail accident was in 1997, when 12 people were killed in Reptowo.
The country's most deadly train disaster dates back to 1980, when 65 people were killed when a freight train collided with a passenger train near Otloczyn.