US Attorney General Eric Holder has met the parents of Michael Brown, the black teenager who was killed by police in Ferguson, Missouri last week.
Earlier, he met officials and toured the town talking to local residents.
Mr Holder has promised a "full, fair and independent" investigation into the killing of Mr Brown, 18, who was unarmed when he was shot.
His death sparked 10 nights of often violent clashes between police and demonstrators.
On Wednesday night, protestors again gathered on the streets of Ferguson, but police said the violence had largely abated since the night before.
Community leaders have continued to appeal for calm and healing.
In an open letter published in the St Louis Post-Dispatch on Tuesday, Mr Holder said that the justice department "will defend the right of protesters to peacefully demonstrate".
However, he added that "violence cannot be condoned" and urged Ferguson residents to condemn "the actions of looters, vandals and others seeking to inflame tensions and sow discord".
He said violent acts had been committed by "a very small minority, in many cases individuals from outside Ferguson".
Reports suggest that Mr Holder is considering opening a broader investigation into policing in Ferguson in general, following several allegations of police misconduct.
The New York Times reports that under Mr Holder, the justice department has ordered more than twice as many such department-wide investigations as before.
Many local residents have demanded that Officer Darren Wilson, who shot the 18-year-old Michael Brown on 9 August, should be arrested and prosecuted. He has been placed on administrative leave with pay.
Witnesses have said Mr Brown was shot as he held his hands up in a position of surrender, while the police and supporters of Mr Wilson have said he fired during a fight with Mr Brown.
The police response, flooding the town with hundreds of officers in riot gear, has been criticised as heavy-handed.
Authorities were also criticised for not being transparent enough in the immediate aftermath of the shooting.
The St Louis County prosecutor's office said it would present evidence against Mr Wilson to a grand jury on Wednesday.
The jury will determine whether or not to charge him with a crime.
A group of protesters gathered in front of the courthouse on Wednesday, chanting, praying and holding up signs urging the county prosecutor to step aside in this case, as a line of police officers stood guard over the main door.
Missouri Governor Jay Nixon has said he would not seek Bob McCulloch's removal.
Both St Louis officials and the US justice department are conducting investigations into the case, which has provoked demonstrations throughout the country.
Police in Ferguson said they arrested 47 people on Tuesday night following a largely peaceful protest.
Missouri Highway Patrol Capt Ron Johnson, who has led the police response since Thursday, said that the protest began without trouble but that during the night some protesters threw bottles of water and urine at police.
"As of 01:00 (06:00 GMT), we have 47 arrests," he said.
However, he stressed that police had not been fired upon and that they did not use tear gas on protesters. "Tonight we saw a different dynamic," he said.
"Tonight the elders in this community, volunteers, activists and the clergy came out in large numbers. They walked, they talked with people. They urged order and common peace," Capt Johnson said.
The relative calm is in contrast to Monday night's violence when Capt Johnson said police came under "heavy gunfire" and responded with tear gas and stun grenades.
This was despite the deployment of National Guard units in the town on Monday.
The police shot another black man on Tuesday in St Louis, in an incident many feared could exacerbate the tension in Ferguson.
He was suspected of robbery, and had approached them brandishing a knife. The second shooting has so far had little or no impact on the protests in Ferguson.
Population of Ferguson, Missouri
Black or black African
6% Police officers are black
21% Families living below the poverty line