Bydgoszcz

The object, which was detected by Polish air defences at the time, was only found in April this year by a passer-by not far from the city of Bydgoszcz in central Poland.

Polish authorities said last month a "military object" had been found in a forest close to the village of Zamosc near the northern city of Bydgoszcz, without going into further details about its origin.

The military prosecutor's office is also investigating what Justice Minister Zbigniew Ziobro described on Twitter as "the remains of an aerial military object" in a forest several kilometres from Bydgoszcz.

Before that, however, he had free rein over altar boys and others in his charge in Bydgoszcz.

It said the source of the leak could be at a military inspectorate in Bydgoszcz, in central Poland, responsible for supplying the military.