BETHLEHEM, Pa. (AP) – Sixteen thousand tons of Bethlehem Steel has collapsed in a matter of seconds as a demolition crew imploded Martin Tower, the defunct steelmaker’s former world headquarters.

WATCH LIVE: The implosion of the historic Martin Tower

Crowds gathered Sunday to watch the demolition of the area’s tallest building, a 21-story monolith that opened at the height of Bethlehem Steel’s power and profitability. America’s second-largest steelmaker went out of business in 2003.

Explosives took out Martin Tower’s steel supports and crumpled the 47-year-old building, which had earned a spot on the National Register of Historic Places despite its relatively young age. The implosion created a dust plume expected to linger for several minutes before settling to the ground.

Martin Tower had been vacant for a dozen years. Its owners are redeveloping the site into a mix of medical offices, stores and apartments.

(Copyright 2019 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)