Hillary Clinton was on Saturday "voluntary" quizzed by US federal prosecutors for three and a half hours as part of a probe that has hung over her White House bid for her use of a private email server as secretary of state.
Her campaign described it as a "voluntary" interview at the Federal Bureau of Investigation headquarters in Washington, DC.
"Secretary Clinton gave a voluntary interview this morning about her email arrangements while she was Secretary," Nick Merrill, spokesman of Clinton Campaign said.
"She is pleased to have had the opportunity to assist the Department of Justice in bringing this review to a conclusion. Out of respect for the investigative process, she will not comment further on her interview," Merrill said.
His use of the word "voluntary" indicates that Clinton was not subpoenaed for the interview.
The FBI is investigating whether the presumptive Democratic presidential nominee and her aides mishandled any classified information on a private email server she used while serving as secretary of state during the first term of President Barack Obama.
Clinton denies handling classified information in her private emails. She said she set up the email address for reasons of convenience.
However, a state department inquiry accused her and other former US secretaries of state of poorly managing email security.
The Justice Department is now seeking to establish whether this constitutes a criminal offence.
The interview signals the bureau's protracted criminal investigation could be entering its final phase, with a long-awaited decision nearing.
