(Reuters) - Thirteen construction workers were hurt on Friday when scaffolding collapsed while they were pouring concrete at a building site in Oakland, California, according to the city’s fire department.

Workers were pouring concrete to create the second floor when the scaffolding gave way, according to Ian McWhorter, a fire department battalion chief.

Some ended up trapped in wet concrete or beneath fallen debris, he told reporters at the scene, according to video footage of a news conference.

Hurt workers were taken to nearby hospitals but no one was seriously injured beyond “a few scrapes and bruises,” he said.

Video footage from the scene showed paramedics tending to workers besides the partially caved-in concrete.

The building under construction is an apartment building, the San Francisco Chronicle reported.