The blaze struck a WB Electronics facility in Skarżysko-Kamienna, south-central Poland, just after midnight, breaking out in the plant's assembly section while the building was closed and empty.
No injuries were reported. Firefighters brought the fire under control in under two hours.
"It wasn't large; the operation lasted less than two hours," said Rafał Maciejczak, a State Fire Service spokesman, describing how crews cut electricity to the building, put out the flames and cleared smoke from the structure.
Detectors were also used to rule out hazardous materials, he said.
Police spokeswoman Anna Sławińska said investigators have taken over the case from firefighters and were examining the scene, including using a drone with a thermal camera to inspect the wreckage.
She said the cause remained under investigation and did not exclude arson as a possibility.
The Internal Security Agency (ABW) has also sent officers to the site, according to Jacek Dobrzyński, spokesman for the government's special services coordinator.
He urged caution against spreading unverified claims about the fire's cause.
"Various narratives are forming, and some people are already describing how this happened; all of this will now be thoroughly clarified," he said, promising further details later.
WB Electronics, Poland's largest private arms manufacturer, produces unmanned aerial systems for the military, including reconnaissance and kamikaze drones used by Ukraine's armed forces.
The affected plant specifically makes pumps for drones and unmanned ground vehicles.
(jh/gs)
Source: Polish Radio, TVP Info