Questions about the possible connection were widely dismissed four months ago. But the FBI's investigation remains open, the sources said, and is in the hands of the FBI's counterintelligence team – the same one looking into Russia's suspected interference in the 2016 election, CNN reported.
One U.S. official said investigators find the server relationship "odd" and are not ignoring it. But the official said there is still more work for the FBI to do. Investigators have not yet determined whether a connection would be significant.
Read alsoCNN: Federal criminal probe being opened into WikiLeaks' publication of CIA documentsThe server issue surfaced again this weekend, mentioned in a Breitbart article that, according to a White House official, sparked President Trump's series of tweets accusing investigators of tapping his phone.
CNN is told there was no Foreign Intelligence Surveillance Act warrant on the server.
Internet data shows that last summer, a computer server owned by Russia-based Alfa Bank repeatedly looked up the contact information for a computer server being used by the Trump Organization – far more than other companies did, representing 80% of all lookups to the Trump server.
It's unclear if the Trump Organization server itself did anything in return. No one has produced evidence that the servers actually communicated.