The U.S. Justice Department launched an investigation Wednesday into alleged civil rights violations by police in a majority Black Mississippi city, stepping in following accusations that officers used excessive force and arrested people without justification. The federal probe will focus on numerous reports from residents of Lexington, a city of about 1,600 people some 65 miles (100 kilometers) north of the capital of Jackson. Assistant Attorney General Kristen Clarke, who leads the Justice Department's civil rights division, announced the investigation at a news conference.