New York City’s police commissioner expressed “strong concerns” on Tuesday about the arrest of an African-American mail carrier who was at work in the Crown Heights section of Brooklyn when he was taken into custody amid an altercation with four police officers.

The arrest of the mail carrier, Glen Grays, attracted national attention after a cellphone recording taken by one of several witnesses at the scene of the March 17 episode was released by the office of Eric L. Adams, the Brooklyn borough president, last week.

The commissioner, William J. Bratton, said on Tuesday that the officers involved in the altercation belonged to the Police Department’s Conditions Unit, a neighborhood-based troubleshooting division that Mr. Bratton described as a preferred assignment.

Members of the unit are expected to work in uniform, Mr. Bratton said, and the officers who arrested Mr. Grays were wearing street clothes. After the arrest, which resulted in Mr. Grays being issued a summons for disorderly conduct, the officers were removed from their assignments and put on patrol pending an investigation by the Internal Affairs Bureau, the commmissioner said.