ST. LOUIS — Protesters blocked rush-hour traffic in both directions on Interstate 70 in the Earth City community of St. Louis County on Monday evening.

Aerial footage from a KTVI-TV helicopter showed lines of protesters joining hands to block the highway as drivers sat in their cars, or got out to watch and wait. Protesters also set out barricades to help block traffic. One driver nosed an SUV through the line of people, with a protester kicking at the vehicle’s door as the SUV pushed against protesters.

Missouri Highway Patrol Sgt. Al Nothum said police departments dispatched troopers and officers to the scene shortly after receiving reports of the shutdown. “It’s a matter of getting them removed and taking down their barriers,” he said of the protesters.

About 5:40 p.m., most protesters cleared off the road and traffic began to move again. Others protesters refused to move and were arrested.

Earlier in the day, police arrested 57 protesters in St. Louis who were demanding the dissolution of the Ferguson Police Department.

Meanwhile, St. Louis County Executive Steve Stenger has declared a state of emergency and turned oversight of the Ferguson situation over to County Police Chief Jon Belmar, in the wake of at least three shooting incidents overnight Sunday.

“Chief Belmar shall exercise all powers and duties necessary to preserve order, prevent crimes, and protect the life and property of our citizens,” Stenger said in a statement issued early Monday afternoon.

Stenger later said in an interview that he has not ruled out imposing a curfew on Ferguson, depending on events Monday night.

The county executive decried the gunfire that marred an otherwise peaceful weekend of protesting around the first anniversary of the 2014 shooting of African-American teen Michael Brown by a Ferguson police officer.

“The recent acts of violence will not be tolerated in a community that has worked so tirelessly over the last year to rebuild and become stronger,” Stenger said. “The time and investment in Ferguson and Dellwood will not be destroyed by a few that wish to violate the rights of others.”

Stenger’s order effectively puts county police in charge of security surrounding the protests, instead of Ferguson police.

“As we work with the St. Louis County Police, who will now assume responsibility over any protest-related incidents … we are asking for peace,” Ferguson Mayor James Knowles III said in a statement. “We want to reassure our residents and businesses that the Ferguson Police Department will continue to answer calls from our citizens.”

Another day of marches began downtown Monday morning after violence marred Sunday’s one-year anniversary of Brown’s death.

About 150 demonstrators gathered at Christ Church Cathedral on Locust on Monday morning to plan a march and discuss methods of civil disobedience.

Then the protesters marched to the Thomas F. Eagleton U.S. Courthouse. After arriving about noon at the courthouse, the protesters were backed by a chanting chorus of “DOJ, do your job,” referring to the U.S. Department of Justice, while they read from a petition that asked the federal government to disband the Ferguson Police Department.

Several of the familiar faces of last year’s Ferguson protests — the Revs. Mike Kinman, Renita Lamkin and Osagyefo Sekou and Rabbi Susan Talve — gave speeches and implored protesters to maintain their fight for justice.

“We have to change the way we do business,” Talve said, calling for an overhaul of the U.S. justice system. She then produced a cruet of holy oil and said, “We’re going to take this oil and spill it everywhere.”

Kinman then implored protesters to dip their hands in it and touch the stones of the federal building.

Shortly before 1 p.m., more than 50 protesters climbed over the barricades that had been set up outside the courthouse and sat down, locked arms and began singing and chanting.

When that move did not produce any arrests after about 20 minutes, the seated group rose and rushed toward the front door of the courthouse, and sat down again. Shortly after that, about 30 members of the St. Louis Police Department arrived on the scene and arrests began.

United States Attorney Richard Callahan said in a statement that 57 people were arrested. He estimated the total number of protesters as being between 100 and 200 and characterized the protest as peaceful. He said those who were arrested would be released after being given summonses.

Those arrested included national activist Cornel West, and protest leaders DeRay Mckesson and Johnetta Elzie. Mckesson is a graduate of Bowdoin College in Brunswick, Maine.

Other protesters near the Old Courthouse used balloons to lift a banner saying “Racism still lives here” over downtown, with the Arch in the background.

On Sunday, more than 1,000 protesters marched peacefully to commemorate the anniversary of Brown’s death, before the scene descended into violence overnight, with multiple shot fired and at least three people wounded.

Kinman, dean at the church, told demonstrators their demands include the disbandment of the Ferguson Police Department. “What we believe is that what happened last night shows the necessity of action of the [U.S. Department of Justice]. Despite the reports and studies that have been done, very little has changed.”

At about 11:15 p.m. Sunday, police shot and critically wounded a suspect who had fired at officers in the 9200 block of West Florissant. Then, about 2:15 a.m. Monday, two males aged 17 and 19 sustained non-life-threatening injuries after being shot by an unknown assailant while walking near a memorial to Brown along Canfield Drive.

Gov. Jay Nixon, in a statement, called Sunday’s violence “a sad turn of events” and called for peace going forward.

“Over the last year, people of good will across the community have worked tirelessly to bridge divisions, restore trust and build a brighter, safer, and more united future for the region,” Nixon said. “For the sake of all, it is my hope and expectation that today’s events will be peaceful so that these efforts can continue to move the region in a positive direction.”

In response to the state of emergency declared by the county, Hazelwood schools announced they were canceling after-school and evening activities Monday.

Stenger, the St. Louis County executive, said in an interview Monday he has not ruled out imposing a curfew in Ferguson and will reassess the situation after observing what unfolds on the streets of Ferguson after nightfall.

“It’s a consideration,” Stenger said. “We’re trying to at least see if the measures in place work first.”

Stenger said he remained in contact with Belmar on Sunday night and into Monday morning as events spiraled out of control on West Florissant Avenue and Canfield Drive, the scene of shootings that left three people injured.

He called the violence that followed a day of otherwise peaceful protests “a personal choice of certain individuals.”

Describing the “volatile situation” in Ferguson as fluid, Stenger said he is equally aware that “every action we take can be second-guessed.”

The county’s priority, he added, continues to be the protection of property, life and the First Amendment rights of individuals peacefully seeking solutions to economic educational and judicial issues that have prompted a second year of discord in North County.

Steve Giegerich, Robert Patrick, Nicholas J.C. Pistor, Joe Holleman, Lisa Brown and Kevin McDermott of the Post-Dispatch contributed to this report.

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