BALTIMORE — The Justice Department said on Tuesday that it will conduct a civil rights investigation into how a 25-year-old man suffered a severe spinal injury while in the custody of Baltimore city police officers and later died.

The federal probe comes one day after the city’s mayor and police commissioner promised to wrap up their own investigation into Freddie Gray’s death by May 1 and allow prosecutors to decide whether criminal charges are warranted. The two investigations can run simultaneously.

Baltimore Mayor Stephanie Rawlings-Blake said in a statement that she welcomes the additional scrutiny to help “get answers to the questions so many of us are still asking” about the case. “Any effort that adds additional transparency and builds community trust in this process is welcomed,” she said in the statement.

Dena Iverson, a spokeswoman for the Justice Department, said in a statement that federal officials have been “monitoring the developments in Baltimore” and that it “opened this matter and is gathering information to determine whether any prosecutable civil rights violations occurred.”

Gray died in a hospital Sunday after lapsing into a coma. Police have said they are not yet sure whether Gray was injured during his arrest or while he was in the back of a police van. Officials have said the officers involved have denied using force during or after the arrest. Six city police officers have been suspended during the investigation.

Residents in West Baltimore remained angry but calm Tuesday. Several hundred protesters took to the streets, but there were no violent incidents. Some Baltimore residents and council members have complained that the police have been too slow to release information and still fell short at a news conference on Monday, when they could not explain how Gray sustained his injuries.