President Donald Trump is relying more and more on his personal, unsecured cell phone to contact outside advisers — a trend that has security experts worried, CNN is reporting.

An unnamed senior White House official told the cable news network that the commander in chief has used the personal phone "a lot more often more recently" and "is talking to all sorts of people on it."

"[It's a] recent development … The walls are breaking," the source said.

Multiple sources tell CNN that Trump's private cell phone usage is an indicator of the waning influence of White House chief of staff John Kelly who has rigorously overseen how Trump communicates in the past.

"Basically, at this point, [Trump is] just sort of engaging on his own. Kelly used to be more clearly the gatekeeper than he is now from a Hill standpoint," another source told CNN.

Mary McCord, former head of the Justice Department's national security division, told CNN: "Use of personal smartphones, which may not have all of the security features of government-issued smartphones or be regularly updated to address newly discovered vulnerabilities, present an obvious potential security risk."