The US Department of Justice has opened an investigation into the death of a black man who died from spinal injuries suffered while in police custody.
The inquiry into the death of Freddie Gray, confirmed to the BBC, will determine whether any civil rights violations occurred.
Gray, 25, died in hospital on Sunday, a week after being arrested in Baltimore.
Hundreds of protesters gathered in the city on Tuesday evening to express their anger over the tragedy.
A national debate over the use of police force has been going on since last summer, when a black teenager was killed in Ferguson, Missouri.
It is not clear why police stopped Gray, but they said they found an illegal switchblade in his pocket.
In a video, Gray can be heard screaming repeatedly as police hold him down.
After his arrest, Gray was placed in a police van for transport to a police station.
At one point during the ride, which lasted about 30 minutes, the van stopped and Gray’s legs were cuffed when an officer said he became “irate”.
He was later rushed to a local hospital where he lapsed into a coma and died a week later.
A court document filed by one of the police officers involved in Gray’s arrest said no excessive force was used in his arrest.
A lawyer for the Gray family said he does not believe the police had a reason to stop him.
Civil rights investigations by the US Justice Department are rare.
Recent examples include the shooting of Michael Brown in Ferguson and the inquiry into the choking death of Eric Garner in New York.
A separate investigation conducted by local authorities is trying to determine how Gray was injured and what happened in the van.
Six police officers have been suspended with pay while this investigation carried out.
Police timeline of the arrest
- Sunday, 12 April, 0839: Officers approach Gray and he flees on foot
- 0840: Gray arrested on corner of Presbury Street, Sandtown
- 0842: Police request a van
- 0854: Van departs with Gray inside, conscious and speaking
- 0924: Police request paramedics to take Gray to hospital
What we know about Gray’s death