(Reuters) - Seven Baltimore police officers were arrested on Wednesday on federal racketeering charges for robbing and extorting up to $200,000 from victims, along with stealing guns and drugs, prosecutors said.

A protester looks on as clouds of smoke and crowd control agents rise shortly after the deadline for a city-wide curfew passed in Baltimore, Maryland April 28, 2015, as crowds protest the death of Freddie Gray, a 25-year-old black man who died in police custody. REUTERS/Shannon Stapleton

Many of the alleged shakedowns took place while the Baltimore Police Department was under intense media scrutiny and facing a U.S. Justice Department civil rights investigation for the 2015 police-involved death of a black man that plunged the largely African-American city into turmoil.

A grand jury last week indicted six detectives and a sergeant on charges of extorting money and robbing residents, filing false court paperwork and making false overtime claims, the U.S. Attorney’s Office for Maryland said. The indictment was unsealed on Wednesday.

“These are really simply robberies by people wearing police uniforms,” U.S. Attorney Rod Rosenstein told a news conference.

The officers, all members in 2015 and 2016 of a gun-crime investigation unit, stole firearms, drugs and cash ranging from $200 to $200,000 from victims, some of whom had not committed crimes, Rosenstein’s office said in a statement.

The investigation began about a year ago as an outgrowth of a federal Drug Enforcement Administration probe into a drug-trafficking ring, Rosenstein said. One of the officers also faces a charge of possessing and planning to distribute heroin.

The officers had initial appearances on Wednesday in a U.S. court in Baltimore and were ordered held pending detention hearings, a spokeswoman for Rosenstein said.

In a statement, Police Commissioner Kevin Davis said: “Reform isn’t always a pretty thing to watch unfold, but it’s necessary in our journey toward a police department our City deserves.”

The head of the Baltimore City Fraternal Order of Police union, Gene Ryan, said in a statement he was “very disturbed” over the charges, but declined further comment until the cases were resolved.

All the officers are charged with racketeering conspiracy for robberies and extortion while part of the gun-crime unit. Five of the seven are charged with racketeering for shakedowns before they joined the task force.

They face a maximum of 20 years in prison for each count.

Baltimore was torn by rioting in April 2015 after a black man, Freddie Gray, died from an injury suffered in police custody. Six officers were indicted, but none were convicted.

Baltimore and the Justice Department reached agreement last month on a consent decree that calls for police reforms. The decree is awaiting approval by a federal judge.