NEW YORK - The New York City police department is investigating whether police officers made offensive comments on a Facebook page devoted to the annual West Indian Day parade in Brooklyn.

Department officials said this week that at least 20 such comments made on the page may have come from police officers. Internal affairs detectives are interviewing officers under oath, and getting subpoenas for computer records. Departmental charges could be brought.

But the posts, however embarrassing or outrageous, also raise a First Amendment free speech issue about whether officers should guard their online comments.