At around five in the morning, in the night between 1 and 2 October, an unidentified object fell near the village of Plauru in Romania's Tulcea County, and a fire broke out immediately afterwards. Romania's Defence Ministry calls it a "possible unmanned aerial vehicle". The spot is just a few kilometres from the Ukrainian bank of the Danube, where that same night new drone attacks were under way against Ukrainian civilian and infrastructure targets.

So far the story sounds familiar. Plauru lies directly opposite an area that has been hit by drones several times in previous years too. What's unusual is the second part of the statement.

"The radar systems of the Ministry of National Defence did not report any unauthorised incursion into national airspace during the past night," the Romanian military said. In other words, Bucharest has an object on the ground it suspects is a drone, but no recorded flight path showing how it entered the country. Something fell from the sky - and the sky, according to the radar, was empty.

The fire has been put out, and the area was immediately secured so that nobody could approach the debris before military experts arrived. No one was killed or injured, and apart from the fire, according to the authorities, there was no material damage either. Romania isn't saying for now whose drone it might be and is not officially linking the object to a specific attack. "The situation is dynamic and we will return with details as soon as they become available," the ministry said.

Romania isn't some distant dot on the map. It is a member of NATO and the EU, it borders Serbia and Bulgaria, and it is separated from the war by literally the width of a river. If something can end up on its territory without the radar lighting up, the question stops being a purely Romanian one.

The key now is the debris. Only after analysis will it be known whether this is a whole drone, part of a drone or something else entirely, and how it ended up near Plauru. Until then, one question hangs in the air, more important even than whose drone it is: if the radar didn't spot this one, how many others have slipped through unnoticed?