The NAACP in Prince George’s County is asking that an outside agency handle investigations within the Laurel Police Department after receiving a series of complaints about officers’ conduct.

The organization’s concerns come after a cellphone video surfaced that showed a handcuffed man being struck in the face by a Laurel officer. The department has kept the officer in the video — against whom a $3 million lawsuit has been filed — on active duty while the case is being reviewed.

“At this point, we’re going to recommend that they no longer do their own investigations,” said Bob Ross, president of the county’s chapter of the National Association for the Advancement of Colored People.

In the past 18 months, Mr. Ross estimates the NAACP has been contacted for advice in at least 20 different cases involving allegations against Laurel police officers. The organization is investigating allegations of inappropriate or illegal action in two cases involving Laurel officers, he said.

“Most of them are routine traffic stops that turn into something else,” Mr. Ross said of cases he’s looked into.