Baltimore (CNN) Baltimore Mayor Stephanie Rawlings-Blake requested Wednesday that the Department of Justice order a "pattern or practice" civil rights investigation into the city's police department, similar to the probe conducted in Ferguson, Missouri after the shooting death of Michael Brown last summer.

The mayor said such a probe was necessary to achieve the kind of "sustainable and significant reform" of the department that she and the citizens of Baltimore want to see.

"The DOJ has employed these investigations in communities across our nation to reform serious patterns and practices of force, biased policing and other unconstitutional practices by law enforcement," she told reporters at her weekly press conference. "I'm asking the Department of Justice to investigate if our police department has engaged in a pattern or practice of stops, searches or arrests that violate the fourth amendment."

The Justice Department is already investigating whether Freddie Gray's civil rights were violated. But the probe Rawlings-Blake is requesting would be far broader, a full-scale civil rights investigation of the entire police department.

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The Justice Department's investigation in Ferguson found systematic discrimination against African-Americans in that city by the police department and the municipal court system, with blacks subject to far more vehicle stops, citations and arrests than their proportion of the population. Blacks were more likely to be searched during traffic stops and cited for minor infractions, and 88% of the cases in which police used force were against African-Americans, who make up 67% of the population of Ferguson.

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