WASHINGTON (AP) -- District of Columbia police say they are investigating an incident in which NBC News reporter David Gregory displayed what he described as a high-capacity ammunition magazine on "Meet the Press."

Police spokesman Tisha Gant said Wednesday the department is investigating whether Gregory may have violated D.C. firearms laws that ban the possession of high-capacity magazines. She declined to comment further.

While interviewing National Rifle Association CEO Wayne LaPierre on Sunday's program, Gregory held an object, apparently as a prop to make a point, and said it was a magazine that could hold 30 rounds.

High-capacity ammunition magazines are banned in the District of Columbia, regardless of whether they're attached to a firearm. "Meet the Press" is generally taped in Washington.

An email seeking comment from NBC was not immediately returned.