A janitor told the BBC a member of Musk's team said his job would eventually be replaced by robots.
Four former Twitter cleaners told the publication they were laid off Monday without severance.
Twitter janitors went on strike Monday after they learned their jobs were in danger.
A member of Elon Musk's team told Julio Alvarado, a janitor who was laid off at Twitter earlier this week, that he'd eventually be replaced by robots, Alvarado told the BBC.
Four former Twitter janitors told the publication they were laid off Monday without severance. Alvarado, who worked as a cleaner at Twitter's headquarters for 10 years, said the tone at the company soured after Musk took over in October.
Since the acquisition, Alvarado said private security had been escorting him around the building while he was cleaning.
"People worked without worries," he told the BBC about the environment at Twitter before the acquisition. "Now we are afraid."
Olga Miranda, the president of the Service Employees International Union Local 87, said she believed the workers were laid off because they were in a union, the BBC reported. The workers organized a strike Monday after they learned the contractor that employed them was set to be replaced.
San Francisco's city attorney, David Chiu, has said he was investigating whether Twitter broke the law. According to San Francisco law, when a company changes contractors for cleaning services, the contractor is supposed to hire workers from the old contractor for at least 90 days during the transition.
Multiple workers told the BBC they were concerned about how they would be able to pay bills in the coming weeks, especially with the holidays coming up.
"Overnight we don't have anything," Adrianna Villarreal, a cleaner who had worked at Twitter since 2018, told the BBC.
"I can only tell you, I don't have money to pay the rent," Alvarado said. "I'm not going to have medical insurance. I don't know what I'm going to do."
A spokesperson for Twitter did not immediately respond to a request for comment.
The company is also being investigated by the San Francisco Department of Building Inspection over reports that Twitter installed bedrooms for workers at its headquarters.
On Wednesday, Musk defended his decision to turn some of Twitter's offices into bedrooms, saying he's "providing beds for tired employees."
Since his acquisition, Musk has fired more than half of Twitter's employees and brought in several workers from his other companies, as well as close business associates, like his PayPal mafia buddy David Sacks and personal attorney Alex Spiro.