WASHINGTON (AP) — Several witnesses have been subpoenaed to appear before a federal grand jury considering charges against former Minneapolis police officer Derek Chauvin, who is already facing state murder charges in the death of George Floyd, a person familiar with the matter told The Associated Press on Wednesday.

The Justice Department's federal civil rights investigation has been focused on Chauvin and some of the witnesses, including other officers who worked with Chauvin, according to the person, who could not publicly discuss the non-public proceedings and spoke to the AP on condition of anonymity.

The New York Times first reported that a grand jury was hearing testimony against Chauvin. The Justice Department declined to comment.

Jury selection begins in Chavin's state case on March 8 — he faces second-degree murder and manslaughter charges — with opening statements scheduled for March 29.

Floyd, a Black man, died May 25 after Chauvin, who is white, pressed his knee against Floyd's neck while he was handcuffed and saying he couldn't breathe. Floyd's death sparked protests in Minneapolis and beyond and led to a nationwide reckoning on race.

Three other officers — Thomas Lane, J. Kueng and Tou Thao — are charged with aiding and abetting second-degree murder and manslaughter and are scheduled to face trial in August. Like Chauvin, all three were fired soon after Floyd's death.

The increased federal grand jury activity in connection with Floyd's death comes as the Justice Department, under President Joe Biden, is expected to focus more on civil rights issues, criminal justice overhauls and policing policies in the wake of nationwide protests over the death of Black Americans at the hands of law enforcement.

At his confirmation hearing this week, Judge Merrick Garland, Biden's nominee for attorney general, emphasized his commitment to combating racial discrimination in policing, telling the Senate Judiciary Committee that America doesn't "yet have equal justice."

Former Attorney General William Barr had previously said that, as is standard department policy, the Justice Department was first going to allow a state prosecution to move forward before the federal investigation would be resolved. It's unclear what specifically prompted the increased grand jury activity in the last few weeks, though most federal grand juries are discharged after about 18 months.

Chauvin was prepared to plead guilty to a state charge of third-degree murder in Floyd's death before Barr personally blocked the plea deal last year, two law enforcement officials with direct knowledge of the talks told the AP. Barr rejected the deal in part because he felt it was too soon as the investigation into Floyd's death was still in its relative infancy, the officials said.

The officials spoke to The Associated Press on condition of anonymity because they were not authorized to publicly discuss the talks.

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Associated Press writer Doug Glass contributed from Minneapolis.