St. Louis police said on Wednesday they had arrested 143 people after they blocked a road as a protest against the recent acquittal of a white police officer in the 2011 death of a black man.
Hundreds of people marched onto Interstate 64 and blocked traffic late Tuesday for several minutes. Police began arresting them as they left the highway.
It is not clear what charges those arrested will face.
Authorities have arrested more than 300 protesters over the Sept. 15 acquittal of former officer Jason Stockley in the shooting death of 24-year-old Anthony Lamar Smith following a high-speed chase.
Protesters and civil liberties groups have accused the authorities of using heavy-handed tactics against demonstrators.
But police say they have had to use a heavy hand because protesters have turned to violence, throwing rocks and other objects at the officers and breaking store windows.
Stockley had been charged with the killing of Smith after a car chase. Prosecutors alleged Stockley also planted a gun on Smith's body, and that video from his car captured the officer saying during the chase that he was going to kill Smith.
The judge in the case said the prosecution had failed to prove the shooting was not a justified use of force in self-defense.
Racial tension in the area is not new. One of the suburbs of St. Louis is Ferguson, Missouri, where two weeks of protests began in August 2014 with the shooting death of Michael Brown, an 18-year-old black man, by a white police officer.
That November, the decision not to indict the police officer sparked another week of protests, and the anniversary of the shooting in 2015 was the occasion of a third protest.