Internal Minister Tomasz Siemoniak has instructed the agency and police to prioritize the investigation, citing concerns over potential sabotage.
"I instructed the Internal Security Agency and the police to investigate the incident with special attention," Tomasz Siemoniak said on Friday.
During a press conference in Warsaw, officials hinted that the fire could be part of a series of hybrid operations conducted by groups inspired by Russia or Belarus.
Siemoniak told reporters that "10 people have been arrested in connection with such activities since the end of January."
He said: "We have been working continuously to try to intercept various pieces of information, prevent threats, and react if a threat arises."
The fire in Sławków broke out around 4:00 a.m. on Friday at a depot containing thousands of liters of diesel fuel, according to reports.
The flames consumed several trucks parked in the area.
Twenty fire brigades were involved in firefighting efforts for several hours. The situation was brought under control around 8:00 a.m.
The Sławków complex includes a facility known as the Euroterminal, the westernmost point allowing transportation of goods from the Far East and Asia to Western Europe.
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Source: PAP/x.com/@MSWiA_GOV_PL