White House officials believe that the personal cellphone of White House chief of staff John Kelly was compromised, possibly dating back to December, according to a report Thursday.

Prior to assuming his position as chief of staff in July, Kelly served as the secretary of the Department of Homeland Security, and as a result, there are concerns about whether hackers or foreign governments obtained information on Kelly's phone during his time in the Trump administration, a report from Politico and the Project on Government Oversight said.

Kelly submitted his phone to White House tech support over the summer and said it hadn't been working properly for months or updating software, which led tech support staff to uncover a suspected breach.

White House aides sent a one-page memo in September through the administration, chronicling the incident.

Kelly reportedly did not use his personal phone often since joining the administration, and instead primarily used his government-issued phone, a White House official confirmed to Politico. Additionally, Kelly does not have or use the phone anymore, and has begun using a new personal phone.

Government officials are unsure when or where the phone was initially compromised and what information, if any, was obtained.

The White House has added storage lockers for personal devices and staffers have been advised to limit personal cellphone use while in the building.

The report comes on the heels of the White House launching an internal investigation into private email use after news broke that members of President Trump's family and senior White House officials had been using private email accounts to conduct work-related business.