President Donald Trump (L) of the United States shakes hands with Russia's Foreign Minister Sergei Lavrov as they meet for talks in the Oval Office at the White House.

Russia's cyber attack on the U.S. electoral system before President Donald Trump took his seat at the White House was much more widespread than people realize, Bloomberg News reported Tuesday.

Since the election, investigations have revealed the invasion of both voter databases and software systems in about two times as many states as was previously reported, the publication said.

It amounts to 39 states targeted, three people with direct knowledge of the U.S. investigation have claimed, according to Bloomberg.

New details on these claims, supported by a classified National Security Agency document recently disclosed by the Intercept, emphasize the scale and scope of this alleged hacking. Investigators are swiftly looking into whether Trump's campaign officials may have colluded in Russia's efforts.

This also paints a "worrisome picture" for future elections, Bloomberg points out.

What could be seen by outsiders as "deep vulnerabilities" in the U.S.'s voting technologies comes less than a week after former FBI Director James Comey warned Congress that the trouble with Russia isn't over.

Though, Russian officials have denied playing a role in any hacking connected to the U.S. elections.

A spokeswoman for the Federal Bureau of Investigation in Washington didn't immediately respond to requests from CNBC for comment.

Read the full story from Bloomberg.