ST. LOUIS — Police arrested 143 people after protesters blocked traffic on a busy highway near downtown St. Louis as part of the ongoing demonstrations against the acquittal of a white former police officer in the 2011 killing of a black man.

Protesters gathered Tuesday evening and marched to Interstate 64, where some walked onto the roadway and blocked traffic for several minutes. Police began arresting people after protesters left the highway.

Police haven't said what charges they will face. A spokeswoman for the Circuit Attorney's office said they likely will be charged in municipal court.

Authorities have made more than 300 arrests at demonstrations 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.

In a lawsuit filed after about 120 people were arrested Sept. 17, the American Civil Liberties Union of Missouri raised concerns about a police tactic known as "kettling," in which lines of officers move protesters into a limited area. The lawsuit also accused police of unnecessarily using of tear gas and pepper spray, arresting bystanders and journalist, and taunting some of those who were arrested.

Police have defended their actions, saying protesters threw rocks at officers, sprayed some with unknown substances and shattered shop windows.

The Rev. Darryl Gray, a protest organizer, was arrested Tuesday for the second time in five days. He was also arrested Friday during a protest near Busch Stadium.

"They kettled us again," Gray said in a phone interview shortly after being released from jail Wednesday. "No one resisted." He said two social media journalists and others not involved in the highway blockage were among those arrested.

By Wednesday afternoon, several of those arrested were still in jail while dozens of other protesters, some with tents, waited on the sidewalk outside for their release. Gray said virtually all of the people arrested were from the St. Louis area.

Protests have occurred in the suburbs, too, including a Sept. 23 demonstration at the St. Louis Galleria shopping mall in Richmond Heights that resulted in 22 arrests.

Earlier Tuesday, St. Louis Circuit Attorney Kim Gardner outlined to a city board a proposal that her office take over and lead all use-of-force investigations involving the police. She asked the Board of Aldermen for $1.3 million to launch an independent team that would include four prosecutors, five investigators and two support staff.

Currently, use-of-force cases are investigated internally by the police department's Force Investigation Unit.

"Both the community and police deserve an objective, fair and transparent investigation, and it is no longer acceptable for police to be essentially investigating themselves," Gardner said.

Lt. Roger Engelhardt, who heads the Force Investigation Unit, said Gardner is "naive" if she thinks her office's credibility also wouldn't be questioned. He stood by the investigations of his unit.

"Every investigation, you have to do the best job you can to be as fair and unbiased as you can," Engelhardt said.