SAN FRANCISCO (AP) — Four construction workers were injured when after wet concrete fell on them as they worked on a multistory building in San Francisco.

Fire Department spokeswoman Mindy Talmadge said concrete being poured on the roof of the six-story building struck the workers around 8 a.m. Wednesday, covering them in sludge. Two of the workers fell about 30 feet after being hit.

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All four men were taken to San Francisco General Hospital, where three of them were listed in serious condition and the fourth in fair condition. Their names were not released.

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The men worked for Nibbi Brothers General Contractors of San Francisco. A message left with the company was not immediately returned.

State workplace safety investigators and city building inspectors were on the scene in the city’s Dogpatch neighborhood to investigate.

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