Polish prosecutors were investigating a "violent release of energy" at police headquarters as the country's top police official confirmed to a radio broadcaster that a grenade launcher that was a present from Ukrainian officials accidentally exploded while he was moving it in his office this week.

Gen. Jaroslaw Szymczyk gave his first comments after the unusual incident to Poland's Radio RMF FM, which reported them on Saturday.

The explosion occurred on Wednesday morning at the national police headquarters in Warsaw. Amid media reporters speculating on the incident, the Interior Ministry issued a statement on Thursday saying that a gift from Ukraine had exploded and that Szymczyk and another person suffered minor injuries.

But the statement left many questions unanswered, including what the present was and who triggered the explosion.

Szymczyk confirmed reports in Polish media that the gift had been a grenade launcher.

RMF FM, citing police officials, said Szymczyk received two used anti-tank grenade launchers as presents during a recent visit to Ukraine. There were no other details, but the report suggested that neither the Ukrainians nor the Poles believed the launchers had any explosive potential. One had been transformed into a loudspeaker.

"When I was moving the used grenade launchers, which were gifts from the Ukrainians, there was an explosion," Szymczyk told the broadcaster. He said the explosion was so powerful that the force of its impact pierced the floor and the ceiling.

Szymczyk was initially hospitalized for observation while the other person, a civilian employee, did not require hospitalization.

Poland is an ally of Ukraine and has offered the neighboring country various kinds of support, including military and humanitarian aid, since Russia's full-scale invasion on Feb. 24. Poland also has accepted a large number of Ukrainian refugees.