Washington (CNN) Justice Department special counsel Robert Mueller is investigating President Donald Trump for obstruction of justice, The Washington Post reported Wednesday evening.

Mueller is interviewing as early as this week three top intelligence officials as part of the probe, the Post reported, citing "five people briefed on the requests."

The three officials the Post says Mueller is interviewing are Director of National Intelligence Dan Coats, National Security Agency Director Mike Rogers and Richard Ledgett, the recently retired deputy NSA director.

Coats will also meet with members of the Senate intelligence committee Thursday, one week after his tense grilling by the panel, according to a committee source.

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It is the most significant sign yet that Mueller's investigation is extending beyond questions of Russian interference in the 2016 election.

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