NEW YORK (ABC News) — Two people climbed to the top of the Empire State Building and unfurled a banner on top of its spire Wednesday afternoon.

The unidentified people appear to be wearing masks.

An NYPD helicopter was sent to the scene and is standing by. The building's observation deck was cleared of visitors as police arrived.

The building's spire is 1,454 feet above the ground.

The two climbers eventually took the banner and made their way down to a lower part of the spire. Once they got to there, one climber appeared to propose to the other before they hugged and took pictures.

The two are now in custody.

This is a developing story. Please check back for updates.