Fresh unrest in Ferguson, Mo., Tuesday night shows that the embers of the month-old unrest surrounding Michael Brown’s death can be kindled by even tiny sparks.

Detectives are investigating how a makeshift memorial to Mr. Brown, an unarmed black teenager killed by white Ferguson police officer Darren Wilson on Aug. 9., burned early Tuesday morning. The memorial, which is one of two near where Brown died on Canfield Drive, included mementos and small candles that may have caused the fire.

But some in the area suggested that it’s “naïve” to think the fire was accidental, and about 200 protesters rallied to West Florissant Avenue again Tuesday, squaring off with police and looting for the third time a store called Beauty Town. There were media reports of looters yelling "Burn it down!" and of gun shots in the area near Canfield Drive. Police made five arrests.

The new unrest and arrests come as Ferguson continues to try to deal with the emotions and issues that surfaced after Brown's death.

A grand jury continues to meet to decide whether Mr. Wilson should face criminal charges for the death of Brown. Last week, Wilson testified for four hours about his role in Brown's death, even as a new video showed witnesses to the shooting appearing perplexed that Wilson fired at Brown. One man called out to police that, "He had his [expletive] hands up!"

Residents have from the first day alleged that Brown was shot after giving up and holding his hands up, but Wilson's supporters have suggested that Brown, who was larger than the officer, punched Wilson, ran away, and then turned around to bull-rush the officer.

The Department of Justice is investigating both Brown’s death and the Ferguson police department over allegations that it violated some residents’ rights by historically over-policing poor blacks.

Meanwhile, the Ferguson City Council on Tuesday moved to reform a court system that has generated city revenue by targeting poorer residents for fines. Nearly every household in Ferguson has an active arrest warrant, mostly for nonpayment of traffic fines or failing to show up for traffic court.

The city council passed three ordinances Tuesday to ensure that court fine revenues make up no more than 15 percent of the city's general revenue. The council tabled a proposal to create a citizen review board of the police department.

But just a few miles away, the violence was flaring again. The new unrest underscored the unresolved mistrust between the town's officials and police force, most of whom are white, and its majority-black population.

In places where trust has been lost, it can often be replaced by paranoia and fear on both sides, says Pamela Oliver, a sociologist at the University of Wisconsin in Madison.

“As you polarize, you circle the wagons, and you put pressure on each other to stick with your own team,” she says. “And if your job has been to enforce, of course you’re going to be feeling scared when the people you’ve been picking on start fighting back.”

Brown’s family and supporters have repeatedly demanded that Wilson be arrested.

The wait for a decision on Wilson has worn thin for some, and Ferguson remains on edge. This week, the city cancelled its upcoming “Street Fest,” a popular community event. The cancellation was “in the interest of public safety,” organizers said. Last Saturday morning, the quaint Ferguson Farmers Market, one of the biggest in St. Louis, was the scene of an altercation between customers and protesters, the St. Louis Post-Dispatch reports.