A spokesman for Donald Trump's campaign said the difficulties that the FBI has faced in working with the Justice Department to investigate Hillary Clinton indicate the Obama administration is improperly trying to affect the outcome of the probe.

On Wednesday, the FBI announced it had opened an investigation into the Clinton Foundation to look into a pay-to-play scheme within the former secretary of state's organization.

"Not only is it completely disqualifying for a candidate for president to be facing two separate FBI investigations less than a week before the election, but the fact that the Obama Administration is so blatantly trying to tip the scales of justice toward Clinton should give every American pause," Jason Miller, Trump's senior communications adviser, said in a statement.

Sources in the FBI said an indictment of Clinton in the pay-to-play case is "likely" despite "some obstruction" from the Justice Department, Fox News host Bret Baier reported Wednesday.