A current White House official has been identified as a person of interest by law enforcement investigating possible collusion between Russia and Donald Trump's presidential campaign, NBC News confirmed, citing two U.S. officials.

The Washington Post first reported the news.

The person in question is a senior advisor in the White House and is close to the president, the Post reported, citing people familiar with the matter.

A Justice Department spokeswoman told the Post that she "can't confirm or deny the existence or non-existence of investigations or targets of investigations." An FBI spokesman declined to comment to the Post.

White House spokesman Sean Spicer said in a statement, "As the President has stated before — a thorough investigation will confirm that there was no collusion between the campaign and any foreign entity."

This development comes on the heels of former FBI Director Robert Mueller's appointment as special counsel for the investigation.

People familiar with the case told the Post that Mueller has already brought on new staff members to the investigation. They said, however, that the case had already increased in significance prior to Mueller's appointment.

Read the full report in The Washington Post.

— NBC News contributed reporting.