D.C. police detain two during a protest in downtown Washington before the inauguration of Donald Trump in January. (Clarence Williams/The Washington Post)

D.C. police officers responding to violent protests at last month’s presidential inauguration may have been overzealous in using crowd-control devices such as pepper spray and “sting grenades” to disperse large groups of people, according to a report issued Monday by a civilian oversight agency.

The Police Complaints Board, which sent monitors to watch how officers handled the demonstrations, also raised questions about the procedures used to arrest 231 people on charges of felony rioting after a group rampaged through a four-block area of downtown, breaking store and vehicle windows and setting fire to a limousine.

In some cases, investigators said rules governing day-to-day policing contradicted regulations for First Amendment gatherings. The complaints board concluded officers did not have clear direction on the use of pepper spray and sting grenades “and they appeared to be deployed as a means of crowd control, and not necessarily in response to unlawful action.”

Mayor Muriel E. Bowser (D) and acting police chief Peter Newsham, who was interim chief during the protests, have defended the arrests and the crowd-control techniques.

Police said in a statement Monday that the department “stands by its assertion that our officers acted responsibly and professionally during Inauguration Day. In response to the riots, the men and women of [the Metropolitan Police Department] made reasonable decisions during extremely volatile circumstances.”

Police said they will consider recommendations by the board. Those include having an independent consultant review the ­actions of police on Inauguration Day and clarifying rules for the use of crowd-control devices.

The U.S. attorney’s office has said most of the arrested protesters used so-called “black bloc” tactics, setting out to cause violence while disguising their identities with ski masks or scarves. Six police officers were injured, including one who was knocked unconscious when a brick or piece of metal thrown by a protester hit him in the head.

While naming Newsham, a 28-year veteran of the force, as her pick for permanent police chief last week, Bowser noted that prosecutors examined each arrest and a grand jury returned indictments against 214 of those arrested. Prosecutors dropped charges against some bystanders and journalists caught up in the arrests, and Bowser said the indictments against all but a handful of those taken into custody demonstrates the police response was sound.

At least one lawsuit against D.C. police that is pending in federal court argues that the arrests were unlawful. And the executive director of the Partnership for Civil Justice Fund, which has been critical of previous police conduct involving demonstrations, calledthe inauguration arrests “yet another illegal dragnet.”

The Office of Police Complaints, the staff of the Police Complaints Board, praised police for the way they handled most demonstrations, including those by people who linked arms to blockade checkpoints at entrances to the Mall and the inaugural parade route. Although a few officers’ badges were not visible and there were scattered reports of misconduct, the monitoring agency said the “overall impression is that MPD performed in a professional manner and effectively and lawfully balanced the interests of public safety with the right to free expression. . . . MPD’s general interaction with the public appeared cordial, helpful and respectful.”

Most criticism was leveled at police handling protests that turned violent at and near Franklin Square and the arrests a few blocks away at 12th and L streets Northwest. The report says demonstrators set off fireworks and were seen throwing bricks and rocks at police and setting fires in the street.

The report documents numerous uses of pepper spray and “stingers,” the sting grenades that produce a loud noise, a flash and smoke and shoot out small rubber pellets that sting but aren’t supposed to embed in flesh. The report says that police protocol for handling demonstrations “does not provide a specific procedure to follow for their use” and is “silent as to whether a warning is required in advance of deploying a less than lethal weapon.”

The complaints board said that in most instances the department’s general orders require officers to give warnings before firing pepper spray. The department “specifically prohibits use of [pepper] spray to disperse a crowd . . . or on a person whom the officer does not have legal cause to take into custody,” the report said.

The oversight board criticized police for making the mass arrest at 12th and L streets, where officers corralled more than 200 people chased from Franklin Square. Protesters and the complaints board said demonstrators were trapped at the corner, were not allowed to leave and were arrested without being given an order or a chance to disperse.

Police have defended that tactic, saying orders to disperse were given previously, while the demonstrators were on K Street. Police said the group did not comply, so police pushed them to 12th and L streets. At that spot, police said, the people were already considered to be under arrest and were detained until they could be handcuffed and processed.