(Reuters) - A Missouri prosecutor on Saturday made public two dozen documents related to the investigation into the shooting of Michael Brown, a black teenager killed by a white police officer, saying his office had inadvertently held them back.

St. Louis County Prosecutor Bob McCulloch released 23 documents, including a transcript of an interview authorities had with Dorian Johnson, who was with Brown in August when the unarmed 18-year-old was shot and killed by Darren Wilson, in Ferguson.

The incident set off days of sometimes violent protests in the St. Louis suburb. A grand jury on Nov. 24 decided not to indict Wilson, sparking another round of protests in Ferguson and other cities calling for reforms in how police use force.

When announcing the decision, McCulloch promised to unseal all evidence presented to the grand jury, excluding some photographs of the crime scene and autopsy.

"Clearly, I inadvertently omitted some material" from the Nov. 24 release, McCulloch said. "I apologize for any confusion this may have caused."

It was the second time McCulloch had released evidence that was left out of dozens of documents and photos on Nov. 24. On Monday, McCulloch made public additional material after he realized they were not part of the initial release.

(This version of the story corrects the spelling of St. Louis County prosecutor's surname throughout to McCulloch, not McCullough.)

(Reporting by Brendan O'Brien in Milwaukee; Editing by Larry King)