WARSAW, Poland (AP) — Poland’s Prime Minister Donald Tusk says an explosion on a railway line linking Warsaw to southeastern Poland was an “act of unprecedented sabotage.” Authorities on Monday were investigating possible connections to Russia, Belarus, or their proxies. The line is crucial for delivering aid to Ukraine. A second area on the same line was also damaged, and further investigation is needed. Polish officials suspect foreign involvement. Western officials have accused Russia and its proxies of staging attacks across Europe since the invasion of Ukraine. Poland has detained multiple people suspected of spying for Russia. No injuries were reported in the incidents.