Police on Sunday were investigating a theft of a city of Long Beach flag that was reportedly stolen outside police headquarters and replaced with a banner supporting President Trump.

An unidentified person allegedly gained access to a secured construction area of the Long Beach Police Department and removed the city flag from a flagpole and replaced it with an "unauthorized political flag," authorities said. A padlock was placed on the flagpole to prevent the banner from being removed.

"LBPD is currently working on identifying the individual/s responsible for this incident," wrote Assistant Chief of Police Wally Hebeish on Twitter. "We are reviewing all available information and evidence and will update this message as facts become available."

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Video released by the department showed a subject crossing the street before entering the construction lot and changing the flag to one that reportedly stated: “Make America Great Again.”

The flagpole was only accessible from a "small, secured parking lot" that houses a construction trailer, police said. Access to the area is limited to primarily construction workers due to the ongoing work being done at the police headquarters parking lot.

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Police said there was no indication the subject is an LBPD employee and they were working with the construction company to locate any witnesses.

Employees with the department would later use bolt cutters to cut the rope and remove the flag.

President Donald Trump speaks about coronavirus testing strategy, in the Rose Garden of the White House, Monday, Sept. 28, 2020, in Washington. (AP Photo/Evan Vucci)

President Donald Trump speaks about coronavirus testing strategy, in the Rose Garden of the White House, Monday, Sept. 28, 2020, in Washington. (AP Photo/Evan Vucci)

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“LBPD is an apolitical organization that does not participate in any political activity that promotes one political party over another," the department wrote in a statement. “Flags or images depicting political activity are not authorized or endorsed by the LBPD.”