Now the firings are being investigated by San Francisco city attorney, David Chiu, to see if the world’s richest person broke the law.
“Elon Musk has had a long history of flouting labour laws,” Mr Chiu told the outlet. “While I’m not surprised this happened, I feel for these workers. We will be looking into this further.”
The cleaners’ union was reportedly told last week that their jobs were under threat and organised a strike on Monday to protest. They were then told that they had all been let go immediately.
“They did this three weeks before Christmas,” said union president Olga Miranda. “I think we were fired because we’re a union.”
Julio Alvarado, who had worked at Twitter for 10 years, said that after Mr Musk’s takeover of the company he would be escorted by private security while cleaning certain areas of the building.
And he says that he was told by someone on Mr Musk’s team that his job would soon become obsolete as human cleaners would eventually replace human ones.
Mr Musk immediately fired Twitter’s top executives when he took over in October, and a week later, fired half the company’s 7,500 staff.
Twitter has been sued by two women who lost their jobs and claim that the layoffs disproportionately affected female employees.
The discrimination lawsuit was filed in federal court in San Francisco on Wednesday, according to Reuters. It stated that Twitter laid off 57 per cent of its female staff, compared to 47 per cent of men at the company.