Protesters chanting "free our people" gathered outside a jail in St Louis after more than 100 people were arrested during protests on Sunday.
Crowds gathered to show solidarity with those who still remain behind bars as demonstrators outside the jail criticised authorities for keeping a number of those arrested behind bars.
Monday was the fourth day of protests over the acquittal of a white former police officer in the killing of a black suspect.
The latest action followed three days of peaceful protests and three nights of vandalism and unrest in the Missouri city that has been rocked since Friday, when a judge announced he found Jason Stockley not guilty in the 2011 death of Anthony Lamar Smith.
Mr Stockley shot Mr Smith after high-speed chase as officers tried to arrest him and his partner in a suspected drug deal.
His mother, Anne Smith, was among those gathered outside the jail on Monday.
Hundreds of riot police were mobilised on Sunday, arresting more than 120 people and seizing weapons amid reports of property damage and vandalism.
The arrests came after demonstrators ignored orders to disperse, police said.
"I'm proud to tell you the city of St Louis is safe and the police owned tonight," Interim Police Chief Lawrence O'Toole said at a news conference on Monday.
On Sunday, more than 1,000 people had gathered at police headquarters and then marched without trouble through St Louis.
By the evening most had gone home, but the hundred or so people who remained grew increasingly agitated as they marched back toward the city centre.
Along the way, they knocked over planters, broke windows at a few shops and hotels, and scattered plastic chairs at an outdoor venue.
According to police, the demonstrators then sprayed bottles with an unknown substance on officers. One officer suffered a leg injury and was taken to a hospital.
During the trial, Mr Stockley, 36, testified he felt endangered because he saw Mr Smith holding a silver revolver when he backed his car toward the officers and sped away.
Prosecutors said Mr Stockley planted a gun in Mr Smith's car after the shooting.
The officer's DNA was on the weapon but Mr Smith's wasn't. Dashcam video from Mr Stockley's car recorded him saying he was "going to kill this (expletive)."
Less than a minute later, he shot Mr Smith five times.
Mr Stockley's lawyer dismissed the comment as "human emotions" during a dangerous pursuit. St Louis Circuit Judge Timothy Wilson, who said prosecutors didn't prove beyond a reasonable doubt that Mr Stockley murdered Mr Smith, said the statement could be ambiguous.
Stockley left the police department and moved to Houston three years ago.