Twitter's rebranding of its San Francisco headquarters has been left hanging after police were called.

The Elon Musk-owned platform is changing its name to X, and attempted to remove the outgoing company name from the offices on Monday.

Five letters had been taken down from the office's large vertical sign before work was interrupted.

It now simply reads "er", mirroring the reaction of some commentators to the firm's abrupt corporate makeover.

Justin Sullivan, who took photos of the sign removal for Getty Images, said San Francisco police put a stop to the sign removal "shortly after it began".

Twitter has been headquartered in the Californian city since 2012, where its sign has become part of the landscape.

Twitter's new logo - an X on a black background - has replaced the famous blue bird on the social network, and was projected onto the side of the headquarters on Sunday.

Mr Musk says "tweets" will be replaced too, with posts to be called "x's" instead.

On Sunday, the billionaire said he was looking to change Twitter's logo, tweeting: "And soon we shall bid adieu to the Twitter brand and, gradually, all the birds."

Local media previously reported that police were called because Mr Musk did not get a permit for the work. However, police later said this was a misunderstanding.

San Francisco police told media it responded to "a possible unpermitted street closure", but it determined no crime had been committed and it therefore was not a matter for the police.

Nonetheless, work did not continue on taking down the sign despite police leaving, and it is unclear when it will recommence.

Mr Musk's decision to change Twitter's well-known name and bird logo has been met with some criticism.

Marketing professor Jean-Pierre Dube told the BBC he thought it was a joke, asking why anyone would "throw away" such a recognised brand as Twitter's.

It has been announced during a period of turmoil at the microblogging site. Mr Musk said advertising revenue has dropped by half and it has faced lawsuits over a failure to make promised severance payments and unpaid bills.

Mr Musk bought Twitter last year for $44bn and, shortly after the takeover, axed thousands of jobs.