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Special Counsel Robert Mueller is investigating President Trump for possible obstruction of justice, five people with knowledge of the situation told The Washington Post.

As part of the expanded investigation into Russian meddling in the 2016 presidential election, senior intelligence officials — including Director of National Intelligence Daniel Coats, National Security Agency Director Adm. Mike Rogers, and Rogers' former deputy Richard Ledgett — have agreed to be interviewed by investigators, possibly as early as this week. Trump had wanted former FBI Director James Comey to publicly announce he was not personally being investigated, and after Comey didn't do so during a House Intelligence Committee hearing, Trump asked Coats and Rogers separately to issue public statements denying any collusion between his campaign and Russia, the Post previously reported. Coats also reportedly told associates that Trump asked him if he could get Comey to step back from the investigation into former National Security Adviser Michael Flynn; he later said he did not feel pressured by Trump to do this.

It's unclear how many other officials have already been questioned as part of the probe. The obstruction of justice investigation started a few days after the firing of Comey last month, the Post reports, and officials are also looking into possible financial crimes committed by Trump associates. A spokesman for Trump's personal lawyer, Marc Kasowitz, told the Post the "FBI leak of information regarding the president is outrageous, inexcusable, and illegal."