Kierwiński said the investigation points strongly toward deliberate sabotage, though he stressed that prosecutors and independent experts must confirm the cause.
"With very high probability, we can say that yes, we were dealing with arson, and now we need to determine who is responsible," he said.
The fire broke out shortly after midnight at a facility operated by WB Electronics, part of the WB Group, one of Poland's largest private defence companies and a major producer of drones.
Security cameras captured a masked person near the site around the time the fire broke out, and investigators are cross-checking additional footage from cameras elsewhere in the area, according to the minister.
He said several unspecified items recovered near the factory could provide further clues.
Kierwiński declined to elaborate on the evidence but suggested it may point beyond a lone culprit.
"There are materials that may indicate we were dealing with an act of sabotage, and they could also help investigators get to the truth, catch this person, and possibly determine who was behind them," he said.
The blaze destroyed warehouse space and caused damage estimated at around PLN 15 million (EUR 3.5 million, USD 4 million), prosecutors said. Those convicted of the offenses could face life imprisonment, they added.
The minister used the case to urge heightened security at companies supplying Poland's military, warning that similar attacks could increase if sabotage is confirmed. He also called on the public to alert police to suspicious activity.
Separately, Kierwiński said the government plans to roll out a new emergency alert app by the year's end, adding to the SMS-based warnings currently sent through the Government Centre for Security (RCB).
The tool, he said, would notify users' phones directly of approaching danger, including in areas without internet access—a feature requiring infrastructure upgrades now being negotiated with telecom operators.
Officials expect the rollout to take several months.
(jh/gs)
Source: Polish Radio