The FBI is widening its investigation of Democratic presidential candidate Hillary Clinton's use of a private email account while she was US secretary of state to determine whether any public corruption laws were violated, Fox News reports.
The Federal Bureau of Investigation has been looking into whether classified material was mishandled during Clinton's tenure at the State Department from 2009-2013.
It will expand its probe by examining possible overlap of the Clinton Foundation charity with State Department business, Fox reported on Monday, citing three unidentified intelligence officials.
"The (FBI) agents are investigating the possible intersection of Clinton Foundation donations, the dispensation of State Department contracts and whether regular processes were followed," Fox quoted one of its unidentified sources as saying.
The FBI and the State Department had no immediate comment on the report.
Republican National Committee Chairman Reince Priebus issued a statement calling the Fox News report "a very troubling development".
Clinton, the front-runner to be the Democratic candidate in November's presidential election, has been criticised for using the private email account hosted on a private computer in her home while secretary of state.
Clinton has said she used communication practices that were widespread across the government. She has said there has been no evidence that she broke the law.