A spokesman for the prosecution would not comment on which other prosecutors have testified for the grand jury.
Ferguson police officer Darren Wilson testified Tuesday for four hours in front of the St. Louis County grand jury investigating the shooting of Michael Brown, the St. Louis Post-Dispatch reported.
According to the newspaper's source, Wilson, who was not required to testify, has been "cooperative" throughout the process, including talking to both county and federal investigators multiple times.
The grand jury was convened on August 20 to decide whether charges should be pressed against Wilson for Brown's death. In addition to witness testimonies, prosecutors will present evidence to the jury such as the cell phone video from the scene released to CNN last week.
While the spokesman for the prosecution wouldn't reveal which other witnesses have testified, attorney Robert P. McCulloch told the Post-Dispatch Wednesday that an audio recording of the proceedings will be made public if there is no indictment.
Wilson fatally shot the 18-year-old on Aug. 9 provoking large protests across the country. The most recent being a vigil led by Brown's parents and the Missouri chapter of the National Action Network Saturday outside the St. Louis County Department of Justice Services demanding Wilson's arrest.