In a complaint, the city of San Francisco says they have visited Twitter headquarters twice since Friday regarding the new flashing "X" sign on top of the building.

According to the complaint, a notice of violation (NOV) was issued for work without a permit for the new sign that adorns the building where the social media platform's headquarters is located.

Owner Elon Musk rebranded Twitter and its iconic bird logo as X last week, as CNN previously reported. He tweeted video of the building with the new flashing "X" logo on Saturday saying, "Our HQ in San Francisco tonight."

"NOV issued for work without permit. Site visited by MH and spoke with Tweeter (sic) representatives and Building maintenance engineer representatives. I explained BID's complaint investigation process and requested access to roof area. Tweeter (sic) representative decline to provide access but did explain that the structure is a temporary lighted sign for an event. I explained to all representatives that the NOV requires the structure to be remove with a building permit or legalize," the complaint reads.

The complaint also noted that on Saturday another attempt was made to access the roof but was also denied.

Patrick Hannan, a spokesperson for the city's Department of Building Inspection told the Washington Post that "to ensure consistency with the historic nature of the building and to ensure the new additions are safely attached to the sign," the city requires a permit to approve new letters or symbols on a sign, the paper reported.

CNN has reached out to the City of San Francisco and X for comment.

According to the city's website, a notice of violation can incur fees, including permit and investigation fees. It is unknown what fees X could face.