The Justice Department’s report on police in Ferguson showed that the “implicit and explicit racial bias” displayed officers there helped foster the unhappy environment that exploded into international view last summer after a police officer shot and killed an unarmed 18-year-old, Attorney General Eric H. Holder Jr. said Wednesday.

Frenzied demonstrations and confrontations between police and protesters dominated the streets of Ferguson after Darren Wilson, a white police officer, shot and killed Michael Brown in August. Seven months after the shooting, which sparked a national conversation on race and policing in the United States, the Justice Department released what Holder described as a “searing” report delving into the city’s police force.

The report highlighted repeated examples of bias in law enforcement and described a system that seemed to be built upon using arrest warrants to force money out of black residents. In addition, the Justice Department also pointed to several racist e-mails written by police and municipal court supervisors and highlighted numerous allegations of physical and bigoted activity on the part of officers.

“Seen in this context, amid a highly toxic environment, defined by mistrust and resentment, stoked by years of bad feelings and spurred by illegal and misguided practices, it is not difficult to imagine how a single tragic incident set off the city of Ferguson like a powder keg,” Holder said during a news conference Wednesday afternoon in Washington, D.C.

In Ferguson, it has become “routine” for officers to violate the constitutional rights of residents, he said. This behavior deepens the distrust that residents say has long existed, as encounters between police and residents “frequently and rapidly escalate and end up blatantly and unnecessarily crossing the line,” he said.

He described the investigation as fair, thorough and rigorous, and vowed to continue working with people in Ferguson and surrounding municipalities, calling the report “only the beginning” of a necessary process. After the Justice Department issued similarly harsh reports on the police departments of Cleveland and Albuquerque last year, city officials in both places reached settlements with the department and promised that reforms would follow.

Holder said that the Justice Department “reserves all of its rights and abilities” to force changes in Ferguson, a reminder that if city officials and federal officials are not able to negotiate a settlement, a federal lawsuit could follow.

“It is time for Ferguson’s leaders to take immediate, wholesale and structural corrective action,” he said Wednesday.

This post has been updated.