As early as 2015, U.S. intelligence agencies overheard Russian government officials discussing people associated with Donald Trump, The Wall Street Journal reported, citing current and former U.S. officials.

Sources told the Journal that the reports weren't revealing or particularly concerning at the time. But one official told the newspaper that U.S. officials were wondering, "What's going on?"

The Journal also reported that investigators are combing through those reports again, in light of the emails released by Donald Trump Jr. on Tuesday.

The president's son made public email exchanges that set up a meeting with a Russian attorney. This lawyer, according to an intermediary, claimed to have incriminating information on Hillary Clinton as part of "Russia and its government's support" for his father's presidential campaign.

The Journal's report comes amid a special counsel and congressional investigations into Moscow's meddling in the 2016 election. Those inquiries are also looking to determine whether the Trump campaign colluded with the Kremlin.

The White House and the president's outside counsel, Marc Kasowitz, did not immediately respond to CNBC's request for comment.

Read the full report in The Wall Street Journal.