Story highlights Trump's aides asked Congress on Sunday to look into whether the Obama administration abused its investigative powers during the 2016 election

Multiple former senior US officials have dismissed Trump's allegations

(CNN) The FBI asked the Justice Department on Saturday to refute President Donald Trump's assertion that President Barack Obama ordered the wiretapping of Trump's phones last year, two sources with knowledge of the situation told CNN.

The FBI made the request because such wiretapping would be illegal, since the President cannot just order the eavesdropping of a U.S. citizen's phones, the sources said. A court would have to approve any request to wiretap. The sources would not say who was involved in the conversations between the FBI and DOJ or what role FBI Director James Comey might have played.

One of the sources said instead of the FBI saying something publicly about the allegations, it was felt it would be more appropriate to ask the Justice Department since the bureau as a policy does not confirm or deny investigations.

The source said it was also felt it would be more appropriate politically to handle this through the Justice Department since Justice officials are freer to talk about such matters with the White House. Before any possible rebuke, it would be expected some conversations with the White House would need to take place.

So far, the Justice Department has not said anything in reaction to Trump's tweets on Saturday, in which he made the wiretapping allegations.

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