WASHINGTON The suburban Washington headquarters of the well-known Discovery channel was locked down on Wednesday afternoon as a gunman reportedly entered the building and held a hostage or hostages.

Montgomery police spokesman Cpl. Dan Friz told newsmen that a report came in about 1 pm of a gunman who entered the building in Silver Spring, Maryland.

The 911 call reported that shots had been fired.

There are some reports that the gunman may have an explosive device but the police spokesman said that hadn't been confirmed.

Some workers from the building have been evacuated.

A day-care centre in the building has also been evacuated. Authorities have sent commandos and sharpshooters to the building and have evacuated some other buildings as well.