Brazilian Supreme Court justice authorizes investigation into president's son

Fabio Luis' lawyer said in a statement on Friday that the defense was unaware of the investigation and had not reviewed any documents or its legal basis, but said there were "suspicions of illegality."

"An investigation is not an exercise in trial and error. That would amount to what we call a fishing expedition, which is unlawful and would lay bare the political interests behind this unusual move," the statement said.

Antunes' legal representatives could not immediately be reached for comment.

In an interview on Thursday, Lula said his son would be investigated like any other citizen and would not receive special treatment. "I will not use my position to protect him," Lula told the Inteligencia Ltda. podcast, adding that he would not interfere in the probe.

The investigation into Fabio Luis has not yet been formally opened, a federal police source said.