A photograph has emerged of Hillary Clinton reading newspapers splashing on Mike Pence's use of a personal email account while in office.
Mrs Clinton appears to be transfixed by the headlines as she learns that the vice president was embroiled in an email controversy.
Mr Pence and Donald Trump repeatedly criticised Mrs Clinton during the presidential election campaign after it emerged she had used her personal emails for her State Department work.
Her use of the private server while she was secretary of state in the Obama administration triggered a huge political fallout and some commentators said it was a major blow to her chances of beating Mr Trump in November's election.
During the campaign, Mr Pence and Mr Trump said Mrs Clinton had broken the law and endangered national security, leading to their backers to chant "Lock her up!" at rallies.
Mrs Clinton was travelling on a flight from Boston's Logan airport in New York on Friday when she was snapped engrossed in the newspapers by healthcare centre worker Caitlin Quigley, who posted the photos on social media.
Emails released under a public records law show that while Mr Pence was the governor of Indiana he regularly used an AOL address to speak to advisers about confidential state business.
His account was later hacked by a scammer asking Mr Pence's contacts for money, according to reports.
Mr Pence's office has confirmed he "maintained a state email account and a personal email account" while governor.
In a statement, his office added: "Mr Pence fully co-operated with Indiana law regarding email use and retention."
The FBI investigated Mrs Clinton's use of a personal email server but she has always insisted she did not use it to send sensitive information.
In July 2016 the FBI said Mrs Clinton had been "extremely careless" in handling classified information but it did not recommend criminal charges.
But just weeks before the election, it revealed it was opening a new probe into the email server after the discovery of new emails in an "unrelated case".