Fire Department Chief James Whitford said 45 Amazon employees survived at the Edwardsville, Illinois facility.
Authorities have given up hope of finding other survivors as they shift from rescue efforts to exhumation efforts that are expected to last for days.
Hurricanes swept through six US states on Friday evening, causing damage to homes and businesses.
Whitford said the Amazon plant was hit by the hurricane at about 8:38 p.m. The wind was so strong that it tore off the roof of the factory and the building itself collapsed.
He added that it was not clear how many workers were still missing, because Amazon did not have an accurate count of the number of people working on the site at the time of the hurricanes.
Colleagues and family members of the workers gathered in front of the ruins of the building, trying to find out any news of their loved ones.
Andy Gacy, Amazon’s chief executive, said on Twitter that the company was “extremely saddened by the loss” of its staff and would continue to work closely with local authorities on the rescue effort.
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