His comments came after revelations that Attorney General Jeff Sessions met twice with Russia's ambassador to the U.S. and failed to disclose those meetings when asked about the topic during his confirmation hearing.
Mr Sessions was an early supporter of the Republican candidate and served as a policy adviser during his campaign.
President Donald Trump has been dogged by questions about his advisers' ties to Russian Federation since the campaign.
A Sessions spokeswoman claimed the Attorney General met with the ambassador in his capacity as a member of the Senate Armed Services Committee and not as a surrogate for President Donald Trump.
Last week, Senate Democrats asked the White House - as well as law enforcement agencies - to keep all materials involving contacts that Trump's administration, campaign, transition team - or anyone acting on their behalf - had with Russian government officials or their associates.
The Washington Post's report was followed up by one in the Wall Street Journal, quoting sources as saying USA investigators have already started examining contacts between Mr Sessions and Russian officials during the presidential campaign.
While the Dutch and British services were warning Washington about these contacts, the US intelligence services also intercepted communications between Russians in which they discussed contacts with people affiliated with Trump and to what extent to interfere in the USA elections.
National Hockey League trade deadline: Lightning trade Valtteri Filppula, acquire, then trade Mark Streit
Removing the emotion from the equation, it's pretty clear that the Tampa Bay Lightning are in fact winners at the trade deadline. Yzerman send Filppula to Philadelphia along with a fourth- and a seventh-round draft pick for Mark Streit .
The Times reporting is gleaned from more than a half-dozen current and former officials, who say the directive did not come from President Obama himself. The official wasn't authorized to discuss the matter publicly and insisted on anonymity.
The U.S. House of Representatives intelligence committee will investigate allegations of collusion between Donald Trump's presidential campaign and Russian Federation, the top Democrat on the panel said on Wednesday.
Trump has denied any of his associates had contacts with Moscow before last year's election and dismissed the controversy as a "scam" perpetrated by a hostile news media.
One official said McGahn's memo instructs White House staff to preserve material from Trump's time in office, and for those who worked on the campaign, relevant material from the election.
"This situation was serious, as is evident by President Obama's call for a review-and as is evident by the United States response", Eric Schultz, Obama's spokesman, said.
House Intelligence members signed off on the agreement Monday evening, setting the boundaries for a high-profile look into the Trump administration's connections to Russian officials during the campaign.