FREDERICK, Md. --

The Federal Aviation Administration says it is investigating a restricted airspace violation by a small plane that came within 30 miles of the nation's capital.

Spokesman Jim Peters said Wednesday the single-engine Cessna 172 was flying from the New York area when it crossed in and out of restricted airspace northwest of Washington several times around 6 p.m. Tuesday.

The FAA alerted the North American Aerospace Defense Command, which says it sent two Coast Guard helicopters to intercept the plane and escort it to the Frederick Municipal Airport.

The FAA holds pilots responsible for knowing about restricted airspaces. Peters says penalties range from a warning letter to a license revocation or fine.