The probe is the first major action of Attorney General Merrick Garland, after President Joe Biden vowed to address systemic racism in the United States.

It will consider whether the department engages "in a pattern or practice of using excessive force, including during protests," he said.

He added it will also examine whether the department "engages in discriminatory conduct and whether its treatment of those with behavioral health disabilities is unlawful."

Chauvin's conviction was a milestone in the fraught racial history of the United States and a rebuke of law enforcement's treatment of black Americans.

Floyd's death was one in a long list of police killings that prompted nationwide protests.

"I know such wounds have deep roots. That too many communities have experienced those wounds firsthand," Garland said.

"Yesterday's verdict in the state criminal trial does not address potentially systemic policing issues in Minneapolis."

Garland has previously said he will make cracking down on police misconduct a priority.

A separate criminal Justice Department investigation into whether the officers involved in Floyd's death violated his civil rights continues, Garland said.

A 12-member jury on Tuesday found Chauvin, 45, guilty of second-degree murder, third-degree murder and manslaughter after considering three weeks of testimony from 45 witnesses, including bystanders, police officials and medical experts.

In a confrontation captured on video, Chauvin, a white veteran of the police force, pushed his knee into the neck of Floyd, a 46-year-old black man in handcuffs, for more than nine minutes in May 2020.

Chauvin and three fellow officers were attempting to arrest Floyd, accused of using a fake $20 bill to buy cigarettes at a grocery store.

The conviction triggered a wave of relief and reflection not only across the United States but in countries around the world.

Australian Associated Press