Mueller met Wednesday with the leaders of the Senate Intelligence Committee in an effort to ensure their investigations don't conflict.
USA TODAY previously reported that the FBI was investigating Kushner for his contact with Russian officials, but there was no word at that time that his financial dealings were part of the probe.
Concerning Trump's reported suggestion to Comey that he should "let go" of the criminal investigation into National Security Adviser Mike Flynn, Comey said, "I took it as a very disturbing thing", adding "but that's a conclusion I'm sure the special counsel will work toward, to try to understand what the intention was there, and whether that's an offense".
In addition, Feinstein has asked Grassley to call Attorney General Jeff Sessions and several other Trump administration officials to testify.
Trump responded to the Post story Thursday morning with a tweet once again denouncing the investigation as a witch-hunt.
'They made up a phony collusion with the Russians story, found zero proof, so now they go for obstruction of justice on the phony story, ' he wrote.
Apparently, Trump believes (or knows?) the report to be correct.
Rod Rosenstein: There's No Reason To Fire Special Counsel Mueller
Collins' question wasn't the only time the Mueller investigation came up during Rosenstein's hearing on Capitol Hill. Indeed, James Comey admitted that Trump wasn't under investigation for collusion (or anything else).
He's been advised of the legal ramifications from making these presidential statements on Twitter, but he and at least a few advisers have come to believe the political fight is more urgent. The newspaper also said Mueller was looking into money laundering by Trump associates.
Trump was alluding to the former secretary of state's handling of her private email server, an issue that dogged the Democratic nominee's presidential campaign since before it officially began.
He also said Comey should have shared his concerns about the Trump conversation with another Justice Department official, Dana Boente, who was then acting deputy attorney general, and would have been Comey's direct supervisor.
The president expressed annoyance about news reports that the probe is now believed to include an examination of whether he obstructed justice by firing FBI Director James Comey, who had earlier led the Russian Federation investigation.
Mr Mueller is leading an Federal Bureau of Investigation inquiry into Russian meddling in the election.
"The FBI leak of information regarding the president is outrageous, inexcusable and illegal", Mark Corallo, a spokesman for Kasowitz, was quoted as saying.
The memo sent Thursday asks for records related to foreign travel, contacts with Russian "officials, agents or nationals" and background investigations into the top Trump associates now targeted by Mueller's probe.
Less than an hour later, Trump sent out another tweet, this one aimed directly at Rosenstein. All week, some of Trump's most ardent defenders, including his son Donald Trump Jr., his White House counselor Kellyanne Conway and friend and occasional adviser Newt Gingrich have questioned the probe in similar ways. As for Comey, he remains a shrewd and calculating defender of the rule of law and its instruments, positioned to defend them against a president he sees as an unprincipled political opportunist in a highly risky time for the country. He said he was untroubled by claims Trump tried to persuade Comey to back off the investigation, saying those revelations only emerged after Comey was sacked and wanted to defend himself.
Kushner has agreed to talk to the Senate Intelligence committee, and is expected to discuss these matters with the Senate intelligence staff, though the timing is still being worked out.