SHREVEPORT - Federal officials are investigating a construction site collapse at a hospital that left nine workers with minor injuries.

Shreveport Fire Chief Scott Wolverton tells KTBS-TV that concrete being poured for an expansion of the Willis-Knighton Medical Center North collapsed when scaffolding and supports gave way Friday morning. Workers say the structure was sagging and they were moving to reinforce it when it collapsed.

Workers were treated at Willis-Knighton North and other hospitals. None of the injuries were life-threatening. Wolverton tells KSLA-TV only "divine intervention" prevented workers from being seriously injured.

Willis-Knighton Health Systems Chief Operating Officer Chuck Daigle says construction is suspended on the $30 million expansion to add an additional intensive care unit, surgery units and hospital beds.

The U.S. Occupational Safety and Health Administration will investigate.