Police in Baltimore say that a van transporting Freddie Gray made a previously undisclosed stop while en route to the police station.
Gray suffered fatal and unexplained spinal injuries while in police custody, sparking two weeks of protests that turned violent earlier this week.
On Thursday, there were rallies in Baltimore, Philadelphia and Cincinnati.
A national debate over the use of lethal police force has been going on since last summer.
Police investigating Gray’s death said they found out about the new van stop from a security camera.
“We discovered this new stop based on our thorough and comprehensive and on-going review of all CCTV cameras and privately owned cameras,” Deputy Police Commissioner Kevin Davis said.
“This new stop was discovered from a privately owned camera.”
The Associated Press reports that the new video came from a Korean grocery shop.
Investigators have handed over their inquiry into Gray’s death to the state’s attorney’s office.
The city’s top prosecutor, Marilyn Mosby, will now decide whether to take the case to a grand jury to seek an indictment of any of the six officers involved.
Gray was injured when arrested in Sandtown on 12 April. He lapsed into a coma and died a week later.
Mobile phone video from a bystander shows two officers dragging Gray into the van by the arms.
According to the police timeline of the arrest, the van took 30 minutes to take him to the police station, where paramedics were called.
While in the van, Gray was requesting medical attention which he was wrongly denied, police have admitted.
They also acknowledged that he was not secured in the van by a seatbelt, which contravenes department policy.
According to a local ABC station, quoting unnamed sources, the medical examiner has concluded that Gray received his injuries inside the van, not when he was first arrested.
Previously, police had said the van made three stops, including one to put him in leg irons and another to pick up another prisoner. The new stop makes four in total.
Five of the six officers involved in the arrest gave statements to investigators the day Gray was injured. All six have been suspended.
A separate investigation by the US Department of Justice is also under way.