The 1,000-square-meter fire has been extinguished.
Several dozen Russian drones were spotted over the oblast overnight.
According to Lutsk Mayor Ihor Polischuk, drone debris was found in several locations across the city.
There were no reported casualties.
Russian forces launched 415 drones and fired 43 missiles at Ukraine overnight. Eight of the drones flew into Polish territory.
Earlier that day, Poland’s military announced that it had shot down drones that violated its airspace during a Russian attack on neighboring Ukraine. This is the first time Poland has taken such a step, which constitutes a major provocation for Europe and NATO forces.
Poland’s President Karol Nawrocki has called an emergency cabinet meeting in response to the airspace violation.
Ahead of the meeting, Poland’s Prime Minister Donald Tusk was consulting with the key ministers responsible for defense and security.
The Polish territorial army says it has shortened the time for reporting for duty and has posted a map.