Elon Musk has criticised San Francisco Mayor London Breed over an investigation into offices turned into bedrooms at Twitter's headquarters.

The city's Department of Building Inspections is investigating potential violations of the building code, local reports say.

Mr Musk accused the city of attacking companies providing bedrooms for "tired employees".

The new Twitter boss recently demanded staff committed to long hours or left.

A Department of Building Inspection official told local public-radio station KQED: 'We need to make sure the building is being used as intended."

In a reply to KQED journalist Ted Goldberg's twitter thread, Mr Musk posted the city should prioritise protecting children from the consequences of opioid drug misuse.

BREAKING: San Francisco building inspectors are launching an investigation into reports Twitter has converted several office rooms at its headquarters into sleeping quarters for employees. 'We need to make sure the building is being used as intended' @sfdbi rep tells @KQEDnews

— Ted Goldberg (@TedrickG) December 6, 2022

Last month, Mr Musk emailed all staff Twitter "will need to be extremely hardcore" to succeed.

"This will mean working long hours at high intensity," he said.

"Only exceptional performance will constitute a passing grade."

And in a now deleted tweet, Mr Musk posted he would work and sleep in the office "until the org is fixed".

'Office armchairs'

Forbes initially broke the story of "sad little conference-room sleeping quarters at the company's recently depopulated headquarters", noting it was an apparent improvement on the improvised sleeping-bag-on-the-floor arrangement posted on Twitter by one employee.

A photo shared with the publication showed "bright orange carpeting, a wooden bedside table and what appears to be a queen bed, replete with a table lamp and two office armchairs", it said.

The bedrooms, Bloomberg reported, are also said to accommodate staff from Tesla and other Musk-owned businesses brought in to work at Twitter, "some of whom travel to Twitter for work meetings", sources told the publication.

Department of Building Inspection official Patrick Hannan told the San Francisco Chronicle it investigated all complaints and there were different rules for residential buildings, even those used for short-term stays.

In May 2020, prior to Mr Musk's takeover, Twitter told employees they could work from home "forever" if they wished to, because its remote-working measures during Covid lockdowns had been a success.

But last month, Mr Musk said remote working would end.