The governor of Missouri has reportedly rejected calls for a new grand jury to decide whether to charge a white police officer for killing a black teenager.
It follows two days of unrest in St Louis and 12 other cities over a ruling not to charge Darren Wilson for the killing of 18-year-old Michael Brown.
But demonstrations appeared to dwindle on Wednesday amid heavy snowfall on the eve of the Thanksgiving holiday.
A handful of protesters remain in Ferguson, where Mr Brown was killed.
The family of Michael Brown said they were left “crushed” by the ruling, which has triggered nationwide debates over relations between black communities and law enforcement.
A spokesman for state governor Jay Nixon said he would not entertain the idea of bringing in a special prosecutor to present the case to a new grand jury, the St Louis Post reports.
Earlier, Mr Nixon said the “ramped up presence” of the National Guard – which more than tripled from 700 to 2,200 on Tuesday night – in the St Louis suburb had been “helpful”.
He said he would continue to monitor the situation to see if more resources were needed.
Earlier on Wednesday, 200 protesters gathered outside St Louis City Hall, holding a mock trial of Mr Wilson. Some of them tried to storm the hall, but were later dispersed by riot police, with at least two people arrested.
By Wednesday evening, only a few dozen protesters remained outside Ferguson Police Department, with some taunting National Guard troops.
Monday’s ruling by a grand jury not to charge officer Wilson led to violent protests and looting in Ferguson, and dozens of arrests.
Anger spread to 12 other cities, including Philadelphia, New York, Cleveland, Los Angeles and Boston.
In Oakland, California, rallies turned violent when protesters started a street fire, while in Los Angeles there were reports of 130 people arrested.
Business owners and residents were seen clearing up the streets of Ferguson on Wednesday.
Some US celebrities are reportedly calling for a boycott to take place on Black Friday – one of the country’s busiest shopping days after Thanksgiving – over the grand jury ruling.
Police officer Darren Wilson has told US media that he had a “clean conscience” over the killing on 9 August.
Mr Brown’s mother said the officer had been “disrespectful” in his comments and that she did not believe his account of events.
In separate comments, the teenager’s father, Michael Brown Sr, said his son’s character had been “crucified” by prosecutors, but also urged protesters to remain peaceful.
Mr Wilson said that before the shooting, Mr Brown had pushed him back into his car, hit him and grabbed at his drawn gun, and said that he felt “like a five-year-old holding on to [US wrestler] Hulk Hogan”.
Mr Brown’s supporters said he was attempting to surrender to Mr Wilson when he was shot.
However, the state prosecutor said physical evidence had contradicted some of the witness statements.
Many in Ferguson’s predominantly African-American community had called for Mr Wilson to be charged with murder, but the grand jury – of nine white and three black members – decided not to charge him.
The decision means Mr Wilson will not face state criminal charges over the shooting. However, the US Justice Department has also launched a federal investigation into whether Mr Wilson violated Mr Brown’s civil rights.