NEW YORK — Even as the New York Police Department sent undercover officers into Muslim neighborhoods to detect possible terrorist activities in the years after the Sept. 11 attacks, government officials there and elsewhere have sought to build relationships in Muslim communities and pledged to ensure that Muslims aren’t targeted for discrimination.

Outreach programs have operated in Boston, Cleveland, Detroit, Minneapolis, Portland, Ore., and Washington — all have large Muslim communities — while law enforcement around the country has stepped up investigative efforts to stave off attacks.