VALLEJO (CBS / AP) — Construction workers rebuilding a bridge in Vallejo on Friday unexpectedly found two people living in a cave dug into an embankment, authorities said.

Crews were excavating at the site of the old bridge in Vallejo when they heard voices and switched off their digging equipment, Tom Walker, the project manager for the city, told the San Francisco Chronicle.

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They discovered a cave about 20 feet long (6 meters) and 3 feet (0.9 meters) high in the side of the embankment.

“We called in the police and fire departments to make sure we didn’t injure anyone” in relocating the occupants, Walker said. “It’s a rescue operation.”

Dozens of police, firefighters and rescue workers converged on the bridge a half-mile north of downtown Vallejo, the Chronicle said.

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Vallejo resident Albert Wong said he saw sleeping bags, backpacks, clothing and other items being removed from the cave.

“It was a lot of stuff,” he said.

“It’s really common to have homeless encampments under bridges but this is the first time I’ve seen something like this,” Walker said.

Construction workers last week began rebuilding a decades-old two-lane bridge that serves Mare Island and hope to have the new span finished by year’s end, Walker said.

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