The unauthorized installation of a giant X sign on the roof of Elon Musk's Twitter headquarters is being challenged by San Francisco building inspectors.

According to Patrick Hannan, building inspector spokesman, permission from the California city’s planning commission and a building permit are both required in order to ensure the sign's structural integrity and safe installation, the San Francisco Chronicle reported.

The department said that the necessary permissions were not given for removal of the “@twitter” letters previously found on the building, and the newly installed X sign is also a security concern.

Last week Elon Musk said that he intends to change Twitter's logo to an "X" from the iconic and beloved blue bird.​​​​​​​

“If a good enough X logo is posted tonight, we’ll make go live worldwide tomorrow,” said Musk, who last year bought the social media website for $44 billion, followed by a plunge in its value, with advertisers fleeing and users complaining of controversial changes.​​​​​​​