SIOUX FALLS, S.D. (AP) — Authorities say a forklift accident touched off a partial roof collapse and fire at a building materials supplier in Sioux Falls.

Employees evacuated Allied Building Products Tuesday afternoon after fire broke out at the business. The Argus Leader says an initial investigation shows a forklift hit a support beam, causing a partial roof collapse and electrical sparks ignited some nearby construction materials.

Officials say the building has heavy damage. Nearly two dozen firefighters were on the scene.

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