LOS ANGELES (CBSLA) — Four people were injured Friday — including three critically — after a fall into a shaft on a six-story building construction site in the San Fernando Valley, authorities said.

The injuries occurred at the site of a building under construction in the 11000 block of Otsego Street in the North Hollywood.

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Four people were injured when they fell three stories at the construction site, according to preliminary reports.

“I was just doing some labor down below and we heard a crash,” said construction worker Chris Olson.

“They were on some kind of plank and it gave way,” Olson said. According to reports, the men were on the plank carrying a heavy piece of metal they were attempting to weld to a wall.

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Construction worker Demetrius Minifield said that type of work is usually done with a crane or lift.

“That’s what they should’ve done,” said Minifield.

Officials with Cal/OSHA were notified of the incident.

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It was initially reported that six workers were injured, two critically.