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The Argus Leader via AP, Joe Ahlquist
Emergency crews clear debris at the scene of building collapse in Sioux Falls, S.D., Friday, Dec. 2, 2016. A fire official says rescue workers are concerned about debris shifting as they try to free two people in the collapsed building.

SIOUX FALLS, S.D. — Rescue workers picked through the rubble of a collapsed building in a South Dakota city Friday in search of two people who were thought to be trapped in the debris.

Crews were concerned about rubble shifting as they carefully worked to free the two. Fire Rescue Chief Jim Sideras said one person trapped in the debris has been talking on the phone with her mother as crews try to reach her.

Sideras said she can't see daylight so rescue workers know she's completely covered by debris.

The other person trapped is a construction worker, Sideras said.

Rescue workers also pulled a dog — alive — from the rubble.

Mike Klatt, 39, was getting coffee across the street when he saw bricks coming down from the top of the building. The bottom gave way, and it collapsed into the street, he said. Klatt said people ran out of the coffee shop to see if anyone was trapped, but nobody was visible.

He said he was waiting at the cordoned-off scene for his black Dodge Magnum to be freed from the rubble.

The building has been vacant since September and was expected to reopen in the spring as a drug store.