Twelve people suffered minor injuries when a building under construction partially collapsed in downtown Oakland in May, burying workers under wet concrete and debris, according to NBC Bay Area TV.

The workers were pouring concrete at about 9:30 a.m. when the floor fell out from under them, fire Battalion Chief Ian McWhorter said.

Oakland Fire Department Deputy Chief Darren White said all the workers were safely extricated after falling 10 to 15 feet into wet cement and getting buried in it and debris. Some workers were left hanging from scaffolding, McWhorter said.

All 12 workers were transported to local hospitals and were treated for minor injuries, which McWhorter described as scrapes and bruises.

"On-site workers did a great job with assisting those under small debris," McWhorter said. Most workers were trapped up to their knee level, he added.

Cal-OSHA and a city engineer are on the scene investigating what caused the collapse.

Source: NBC Bay Area    www.nbcbayarea.com