STORY: This CCTV footage shows the moment Bulgaria used a controlled blast to destroy explosives on a device attached to a drone.
The aircraft is believed to be connected to Russia's war against Ukraine - although it's unclear where it came from.
The drone was found on Sunday - on the shores of a Black Sea resort town.
The next day, a Bulgarian army unit checked the site out and determined the drone couldn't be moved with the explosives still attached.
The NATO-member country's defense minister says it can be assumed the drone is linked to Russia’s war against Ukraine.
"First, we're talking about an aerial drone, it's possible that it fell into the water, but I can't say at the moment,” Todor Tagarev said on Monday.
He noted the war is bringing increasing risks to Bulgaria’s security.
The area where the drone was found is about 40 miles south of the Romanian border - and across the Black Sea from Crimea.
That’s the Ukrainian peninsula that Russia forcibly annexed in 2014.
Now, it’s a regular target of Ukrainian drone attacks.
Last week, fragments of a suspected drone were found in Romania…
after a new Russian attack on Ukraine’s Danube ports across the border.