Private broadcaster RMF FM said authorities believed the object could be part of an air-to-surface missile that most likely belonged to the Polish army.
Prosecutors probing the case said that "no traces of explosions or explosives were found at the site."
They added in a statement that "various hypotheses regarding the secured evidence" were being investigated.
The statement came after Polish authorities said earlier in the day that the remains of an unidentified “aerial military object” had been found in a forest near the north-central city of Bydgoszcz.
The Polish defence and justice ministries did not identify the object or say how long it had been there, the Reuters news agency reported.
The Polish defence ministry wrote on Twitter on Thursday morning: “The remains of an unidentified military object have been found in the vicinity of the village of Zamość, some 15 kilometres from Bydgoszcz.”
The tweet added that "the situation does not threaten the safety of residents” and “the location of the discovery is being investigated" by Polish officers and military police.
Meanwhile, Justice Minister Zbigniew Ziobro announced that prosecutors had launched a probe into the discovery, public broadcaster Polish Radio’s polskieradio24.pl website reported.
The scene of the investigation in a forest near the north-central Polish city of Bydgoszcz. Photo: PAP/Tytus Żmijewski.
Ziobro said in a tweet: “The military department of the District Prosecutor's Office in Gdańsk, under the supervision of the National Public Prosecutor's Office, has initiated proceedings regarding the remains of an aerial military object found in a forest several kilometres from Bydgoszcz."
The justice minister added that military experts, police and security services had been deployed to the scene, according to polskieradio24.pl.
The area where the object was found is hundreds of kilometres from Poland's borders with Ukraine, Belarus and the Russian exclave of Kaliningrad, Reuters reported.
Photo: PAP/Tytus Żmijewski
Thursday is day 428 of Russia’s war on Ukraine.
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Source: IAR, PAP, polskieradio24.pl, Reuters