FBI obtains warrant to search newly found Hillary Clinton emails

The Federal Bureau of Investigation (FBI) has obtained a warrant to begin reviewing newly discovered emails that may be relevant to the Hillary Clinton email server investigation, a law enforcement official has said.

FBI investigators want to review emails of longtime Clinton aide Huma Abedin that were found on a device seized during an unrelated sexting investigation of Anthony Weiner, a former New York congressman and Abedin's estranged husband.

The official, who has knowledge of the examination, would not say when investigators might complete the review of Abedin's emails but said they would move expeditiously.

The Clinton email enquiry, which closed without charges in July, resurfaced on Friday when FBI Director James Comey alerted members of Congress to the existence of emails that he said could be pertinent to that investigation.

The FBI wants to review the emails to see if they contain classified information and were handled properly, the focus of the earlier Clinton enquiry.

Separately on Sunday, another law enforcement official said FBI investigators in the Weiner sexting probe knew for weeks about the existence of the emails potentially related to the probe of Clinton's server. A third law enforcement official also said the FBI was aware for a period of time about the emails before Comey was briefed, but wasn't more specific.

In his letter that roiled the White House race, Comey said he'd been briefed on Thursday about the Abedin emails and had agreed that investigators should take steps to review them.

It was not immediately clear on Sunday what steps investigators took once the emails were first found to fully advise FBI leaders that additional and potentially relevant messages had been discovered.

The officials were not authorised to discuss the matter by name and spoke on condition of anonymity.

The timing of Comey's letter less than two weeks before Election day drew criticism from Democrats and some Republicans who cast it as unprecedented and as potentially tipping the scales in the presidential race in favour of Republican Donald Trump.