The US justice department and attorney general Loretta Lynch reportedly does not approve of the timing of the FBI reopening the probe into Hillary Clinton's use of a private email server

FBI director James Comey sent a letter to members of Congress on 28 October, informing them the FBI had learned of the existence of emails that appeared to be pertinent to the investigation into Clinton's use of a private email server, and would be re-opening the probe.

But a source told The Hill the timing of the investigation went against the wishes of the justice department, whose stance is to avoid taking any action that could affect the election.

"The Attorney General's position is consistent with the department's position not to take investigative steps that would influence an election so close to the election and to not comment on ongoing investigations," the anonymous source said.

"Director Comey decided to operate independently of that guidance by sending that letter to the Hill."

Clinton herself also commented on the timing of the probe in comments she made at a press conference in Des Moines, Iowa.

"We are 11 days out from perhaps the most important national election of our lifetimes," she said. "Voting is already underway in our country, so the American people deserve to get the full and complete facts immediately."

Clinton also confirmed to the media she had not been contacted by the bureau in advance of the letter being sent out to members of Congress, and urged the FBI to make the full facts available immediately.

"So we don't know the facts, which is why we are calling on the FBI to release all the information that it has," she explained. "Even Director Comey noted that this new information may not be significant, so let's get it out."

Clinton's rival Donald Trump has praised the re-launch of the investigation, while his campaign manager said the news had been "a great day" for his campaign.