Sullivan & Cromwell told a US federal bankruptcy court that a major filing it made in a high-profile case contained multiple “hallucinations” made by AI software.

Andrew Dietderich, the head of S&C’s restructuring practice, apologised in a letter to New York federal judge Martin Glenn on Saturday for mistakes that included misquoting the US bankruptcy code and citing cases incorrectly in a court filing made on April 9.

“We deeply regret that this has occurred,” he said in the letter.