Eric Holder, who served as attorney general under former President Barack Obama, warned President Trump against trying to hinder special prosecutor Robert Mueller's probe into Russian meddling in the 2016 election after it was reported Thursday evening that Trump's legal team is considering it.

"There is NO basis to question the integrity of Mueller or those serving with him in the special counsel's office. And no conflicts either," Holder tweeted.

There is NO basis to question the integrity of Mueller or those serving with him in the special counsel's office. And no conflicts either — Eric Holder (@EricHolder) July 21, 2017

He added, "Trump cannot define or constrain Mueller investigation. If he tries to do so this creates issues of constitutional and criminal dimension."

Trump cannot define or constrain Mueller investigation. If he tries to do so this creates issues of constitutional and criminal dimension. — Eric Holder (@EricHolder) July 21, 2017

The Washington Post reported that Trump has asked his advisers about the scope of his pardoning power, including for aides, family members, and even himself in connection to Mueller's Russia investigation. His legal team is also reportedly examining ways to build a conflict-of-interest case against Mueller.

Mueller's investigation, along with several congressional probes, is looking into Russian interference in the 2016 election and possible ties to the Trump campaign. The special prosecutor's team also reportedly may be checking whether Trump obstructed justice, and on Thursday Bloomberg reported that the probe is parsing through Trump's business dealings.

Asked by the New York Times on Wednesday if Mueller diving into his personal finances would be a step too far, Trump said, "I would say yes." Though he didn't say what he would do about it, he did add, "I think that's a violation. Look, this is about Russia."

Trump and his allies have also expressed concern about some people in the Mueller team who had donated to Democrats, including Hillary Clinton, who was Trump's Democratic opponent in the 2016 election.

Mueller was appointed by the Justice Department to run the federal Russia probe after Trump fired FBI Director James Comey.

Amid the fallout Thursday evening, the spokesman for Trump's outside legal team, Mark Corallo, resigned. He reportedly had opposed publicly defaming Mueller and became unhappy with the discord in and around the White House.