Argentine President Mauricio Macri has pledged to assert his innocence when he appears before a federal prosecutor to explain his financial dealings.
An investigation began on Thursday after it transpired Mr Macri was mentioned in the Panama Papers, leaked files of law firm Mossack Fonseca.
According to local media reports, Mr Macri was listed as director of an offshore company in the Bahamas.
In a TV address, President Macri vowed to prove he had done nothing wrong.
He said he wanted to co-operate fully with any inquiry.
“I know there are some people concerned about these allegations in the Panama Papers that have come out and involve me,” he said.
“I want to say one more time that I am very calm, I have complied with the law, I have told the truth and I have nothing to hide.”
The president said that he had made clear in his initial declaration that he did not have any shares and did not receive any payment for acting as a director of offshore companies.
He said that on Friday he would be submitting a judicial “declaration of certainty” so that prosecutors can see he is telling the truth.
Mr Macri’s office has insisted that he had no shares in the company in question and never received any income from it.
Argentina’s national tax authority and anti-corruption office will be asked to provide information to the inquiry.
Prosecutor Federico Delgado said he wanted to determine if Mr Macri had “omitted, with malicious intent” mentioning his reported role in the Bahamas-registered offshore company Fleg Trading.
La Nacion, one of the newspapers examining some of the leaked documents, reported that Mr Macri was listed as a director of Fleg Trading from 1998 until 2009.
Mr Macri did not list the company in his 2007 financial declaration, when he became mayor of Buenos Aires, or in his 2015 declaration when he became president.
On Tuesday, Mr Macri’s office confirmed that a business group owned by the president’s family had set up an offshore company through the law firm at the centre of the Panama Papers scandal.
But his office argued that because he had never received any income from it there had been no reason to mention it in the financial declarations.
Mr Macri campaigned on a promise to combat corruption.