Mrs Clinton reportedly told donors that analysis of polling by her team showed Mr Comey's intervention to be pivotal
Hillary Clinton has reportedly blamed FBI director James Comey for her surprise defeat in the US election.
She pointed the finger during a conference call with her top campaign funders, according to two participants in the call.
Mrs Clinton led in almost every poll before America selected Donald Trump as its 45th president, despite FBI director James Comey's announcement 11 days before the election that he was once again investigating her private email server.
But the former First Lady, who has kept a low profile since her concession speech on Wednesday morning, told donors that analysis of polling by her team showed Mr Comey's intervention to be pivotal.
It caused an erosion of support in the upper Midwest, according to people familiar with the call.
Mrs Clinton lost in Wisconsin, the first time since 1984 the state favoured a Republican candidate.
Michigan, where the final result has still not been tallied, also leaned Republican.
Just days before the election Mr Comey announced the new investigation had found no criminal activity - but Mrs Clinton's narrative is that the damage had been done.
She told donors that her rival was able to attack her following both announcements.
Mr Trump claimed after the investigation was dropped that the system was "rigged".