MARICOPA, Ariz. (AP) – Three workers are being treated for severe burns after corn dust exploded at a silo south of Phoenix.

Maricopa police Sgt. Stephen Judd says employees were offloading corn dust into a pit Monday morning when the blast occurred.

The three injured workers have been taken by helicopter to a hospital burn unit with second- and third-degree burns, mostly to their faces, arms, and hands.

Judd says the men were in stable but serious condition Monday.

He says it’s unclear what ignited the corn dust but that the explosion was so powerful it tore steel anchoring rods out of concrete. There was no fire after the explosion.