Wouldn't Manafort's overtures to Russian billionaires and Donald Trump Jr.'s secret meetings with former Russian spies be the sort of thing someone with Pence's level of responsibility should know about?
Mueller has requested that the White House turn over all internal communications and documents related to the Federal Bureau of Investigation interview of Flynn in January, days after he took office, as well as any document that discusses Flynn's conversations with Russian Ambassador Sergey Kislyak in December.
The retired lieutenant general was sacked in February after it was revealed he misled Vice President Mike Pence about December phone calls he had with the Russian ambassador at the time Sergey Kislyak.
Former chief White House ethics lawyer Richard Painter told Chris Matthews that the "the obstruction of justice and the lying" may be what brings down Donald Trump's presidency.
Lawyers for the White House are in the process of trying to cooperate with the document requests.
Mr Mueller has also requested documents about the circumstances of the firing of former National Security Adviser Michael Flynn, the Times said.
There have been several indications that Mueller's investigation is not simply escalating, but also increasing its scrutiny on how the Trump White House has handled matters pertaining to Russian Federation.
A statement given to journalists in July - which the White House said Trump had had a hand in drafting - said the meeting was primarily about a U.S. program for adopting Russian children.
"So what happened with respect to that meeting is critically important, as well as what happened with respect to firing James Comey, the FBI Director. He was insane, a real nut job", Trump reportedly said during the May conversation in the Oval Office, according to the Times.
The White House is committed to fully cooperating with the special counsel, he added.
He said it would be obstruction of justice if Trump fired Comey to stop the Russian Federation investigation, the HuffPost reported. Mueller is apparently not content to just look at their words alone, but is willing to examine outside evidence that could point to whether or not Trump acted with "corrupt intent" when he fired Comey. They are also interested in details of the conversation between then-deputy attorney general Sally Yates who raised concerns about Flynn with White House counsel Don McGahn in late January.