ST. LOUIS — On edge after a night of protests that led to dozens of arrests and a broken window at the mayor’s home, this city faced more demonstrations on Saturday after the acquittal of a white former police officer who shot and killed a black driver.

Tensions here have seemed especially high, in part because the region has been at the center of the nation’s debate over police treatment of black people. St. Louis is about 10 miles south of Ferguson, where unrest erupted three years ago after another police shooting.

City and state law enforcement officials repeatedly struck a note of warning on Saturday, promising that they would not tolerate violence during the protests.

Just after 9 p.m., a two-hour march that had meandered through University City, a St. Louis suburb, came to a peaceful end. However, about two hours later, when the police ordered a group to disperse, some people in the group would not let the officers make it to their vehicles safely and several individuals began throwing bricks and water bottles filled with paint thinner and gasoline, the police said in a statement.