The blast destroyed a section also used to transport weapons to Ukraine. Prime Minister Donald Tusk said it was an "unprecedented act of sabotage" that could have ended tragically.
Tusk stated on Tuesday that two individuals responsible for the sabotage had been identified. He added that they are Ukrainians who collaborated with Russian intelligence and fled to Belarus.
At the same time, he announced that a higher threat level would be introduced on selected railway lines and that the military would be deployed to protect key infrastructure.
"The head of the Internal Security Agency and the interior minister have asked me to introduce the third threat level, known as Charlie, due to the terrorist threat," Tusk told parliament. "This level will apply to certain railway lines, while the rest of the country will remain at the second alert level."
Kremlin spokesman Dmitry Peskov rejected responsibility for the incident. "Russia is being blamed for all manifestations of the ongoing hybrid and direct war," he said. "In Poland, let's say, everyone is trying to run ahead of the European locomotive in this regard. And, of course, Russophobia is flourishing there," he added.
Emergency services and prosecutors intervened at the scene, while further damage was also found closer to Lublin.
The defence minister informed that the army was checking 120 km of track leading to the Ukrainian border. Warsaw has long warned that its logistical assistance to Ukraine makes it a target for Russian diversion.
Already in October, Polish and Romanian authorities detained eight people suspected of planning sabotage on behalf of Russia. Moscow denies any responsibility.
But Poland vows to track down the perpetrators regardless of their backers.
(reuters, swag)