(Bloomberg) -- Investors in Cerebral Inc., the online mental health startup that’s the subject of a federal investigation into its prescribing practices, have pushed to dismiss its founder and chief executive officer, Kyle Robertson, according to people familiar with the matter.

Robertson remains CEO, though his access to the company’s internal communications systems was revoked late Monday, said one of the people, all of whom requested anonymity discussing the attempted ouster.

News of the power struggle emerged just hours after Cerebral said late Monday night that its clinicians would no longer prescribe most controlled substances. The company didn’t immediately respond to requests for comment.

Cerebral, which is backed by investors including SoftBank Vision Fund 2, Len Blavatnik’s Access Industries and WestCap Group, has been valued at $4.8 billion. In a Bloomberg Businessweek story that was published in March, dozens of the company’s clinicians and other staff expressed fears that the company was over-prescribing the amphetamines used to treat ADHD.

Agents from the federal Drug Enforcement Administration have spoken with at least two Cerebral employees about its handling of controlled substances, according to two people familiar with the conversations. The company confirmed it was subpoenaed by the US Attorney’s office earlier this month. A spokesperson said at the time that “no regulatory or law enforcement authority has accused Cerebral of violating any law.”

In an email sent to employees on Monday afternoon, Robertson said the company’s decision to stop prescribing most controlled substances was the result of “the evolving landscape around the accessibility of mental healthcare, and the ability for patients to return to an in-person or hybrid care model.”

A copy of Robertson’s email was reviewed by Bloomberg News. He wrote that Cerebral will discontinue controlled substance prescriptions for new patients beginning on May 20 and for existing patients on Oct. 15. He said Cerebral will continue to prescribe Suboxone and Narcan, which are treatments for opioid addiction and overdoses.

(Updates with additional detail, beginning in second paragraph)

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