WINSTON-SALEM, NC (CBS News) — Residents in the area near a North Carolina fertilizer plant that caught fire Monday night are urged to stay away from their homes for an “undetermined” amount of time, as a massive amount of ammonium nitrate within the burning facility is at risk of an explosion, officials said Wednesday.

“At the beginning of this incident there was enough ammonium nitrate on hand for this to be one of the worst explosions in U.S. history,” Winston-Salem fire chief William “Trey” Mayo said at a press conference Wednesday.

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The fire broke out at about 6:30 p.m. on Monday at the Winston Weaver Company Fertilizer plant in Winston-Salem, North Carolina. No injuries have been reported and all employees are accounted for, officials said.

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According to Mayo, there were nearly 600 tons of ammonium nitrate and 5,000 tons of finished fertilizer at the facility.

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