Compiling 52 accusations of violations of the freedom of the press during the protests in Ferguson, Mo., after the killing of Michael Brown, the PEN American Center will announce on Monday that it is calling on the Justice Department to investigate the local police forces’ treatment of the news media.

Such an investigation, a report by the organization said, would “shed essential light on the factors that drove law enforcement officers in Ferguson to infringe on media freedoms,” and should lead to new guidelines from the Justice Department for police departments in the United States “on respect for media freedoms during public demonstrations.”

A copy of the report, which is to be released on Monday, was made available to The New York Times.

The PEN report described a range of police interference with journalists who covered the protests that followed the fatal shooting on Aug. 9 of Mr. Brown by Officer Darren Wilson of the Ferguson Police Department. Mr. Brown, 18, was not armed.

The examples in the report included the decision to hold reporters in areas that denied them access to the events they had come to cover, and accusations of flashing lights to hinder photographers and of threats and assaults, culminating in the arrest of 21 journalists.

Most of the episodes occurred from Aug. 12 through Aug. 20, according to the report, which was based on news accounts, photographs and videos of the protests, Twitter feeds by journalists and interviews.

US Inquiry Sought in Police Treatment of Press at Ferguson Protests