On Monday, FBI Director James Comey testified before Congress to say that the FBI was investigating the possibility that associates of Donald Trump may have colluded with Russians in order to coordinate the release of information on Hillary Clinton during the 2016 presidential election.

U.S. officials spoke to CNN concerning the investigation, saying that the information being uncovered suggests the possibility that Trump associates did, in fact, coordinate with a foreign country during the election, but they stressed that the evidence was not conclusive and that the investigation is still ongoing.

Still, according to one law enforcement official, the evidence suggests that “people connected to the campaign were in contact and it appeared they were giving the thumbs up to release information when it was ready.”

The FBI has already been investigating four former Trump campaign associates, which include former NSA director Michael Flynn; Paul Manafort, Trump’s former campaign manager; Trump political consultant and longtime friend, Roger Stone; and Carter Page, the campaign’s foreign policy advisor, whose role¬†campaign staffers later denied amid suspicions surrounding Russia.

The four former Trump associates have reportedly been in contact with Russians known to U.S. intelligence. All four have denied having improper contacts.

On Monday, after Comey’s testimony to Congress, White House press secretary Sean Spicer insisted that there was no evidence to prove that collusion took place, saying, “Investigating it and having proof of it are two different things.”

The information is not being drawn from the leaked dossier that was compiled by a former British intelligence officer, according to U.S. officials. Additionally, officials say that one of the problems facing the investigation is the fact that, given the scrutiny that many in the Trump camp have come under for their communications with Russia, Trump administrators have stopped communicating with the Russians, and the Russians have changed their methods of communication as well.