Bulgaria's Defense Minister says the drone was of a type "often used by the Ukrainian military," and it was reportedly equipped with a "considerable" amount of explosives.
The Ukrainian ambassador to Bulgaria has been summoned.
"We can say with certainty that the Ukrainian armed forces have not intentionally fired any weapons at Bulgaria," a spokesperson for the Ukrainian Foreign Ministry said.
No one was injured in the explosion. An analysis by the Bulgarian Defense Ministry shows no indication that the incident was intentional. The drone crashed in a sunflower field.
Drone incidents have become more common in recent months in NATO countries in Eastern Europe.
