The National Public Prosecutor's Office said it was seeking to establish whether others had assisted the suspect in fleeing and avoiding criminal responsibility.
Ziobro, a senior MP for the Law and Justice (PiS) party, said he had not fled Poland and was travelling on a document linked to asylum status granted to him.
He confirmed his presence in the US in an interview with a right-wing television channel.
Polish media have reported that his former deputy, Marcin Romanowski, has likewise left Budapest for the United States.
Both men had allegedly been sheltering in Hungary, where Viktor Orbán's government granted them international protection in December last year.
Reports suggest they left Budapest following Hungary's parliamentary elections on 12 April and the transfer of power to the opposition on 9 May.
Ziobro faces charges over alleged irregularities in the Justice Fund, a state scheme aimed at supporting crime victims.
In late 2025, parliament approved his detention and the prosecution issued an arrest warrant – only to find he had already left Poland for Budapest.
A European arrest warrant request against him is currently before a court; a separate warrant against Romanowski was reissued in mid-February.
Poland's foreign ministry said it would ask both the US and Hungary to clarify the legal basis for Ziobro's departure from Hungary and his admission to the United States.
Spokesman Maciej Wiewiór said there were currently no plans to summon the US ambassador, adding that he hoped the situation would not affect what he described as "the very good bilateral relationship" between the two countries.
Deputy Defence Minister Paweł Bejda suggested Ziobro had not organised his departure alone, saying he "had friends who helped him".
(ał)
Source: tvp.info