Polish authorities say an explosion on a railway line near the Ukraine border was a deliberate act of sabotage, with no casualties reported, and Prime Minister Donald Tusk vowed to find those responsible.

The attack occurred on a crucial route for military and humanitarian aid to Ukraine, with a second suspicious incident on the same line likely linked to sabotage.

Officials suspect foreign involvement, possibly from Russian intelligence, given Poland’s history of hybrid attacks, including parcel bombs and espionage targeting railway infrastructure.

Investigators are collecting evidence from security cameras and other sources, but no suspects have yet been detained, the BBC has reported.

Experts suggest the attack may have been intended to intimidate Poland psychologically, and officials stressed they would pursue the perpetrators “ruthlessly.”