Eleven construction workers were injured yesterday afternoon, one critically, when a building under renovation collapsed in East Williamsburg, officials said.

The workers were adding 1,000 square feet of space to a three-story brick building at 103 Meserole St. when, around 1 p.m., its side walls fell in, burying two workers under piles of wood, cinderblock, and brick, building and fire department officials said.

Neighborhood residents said they heard a big crash.

“It was like a big explosion,” said Miranda Mercedes, who lives down the street. “There was a lot of dust, black smoke, screaming.”

Firefighters pulled two men from under the rubble and evacuated them through the building’s backyard, fire Chief Edward Kilduff told reporters at the scene. Other workers were able to walk out of the building, he said.

Four workers were in stable condition with relatively minor injuries, while seven were hospitalized with more serious injuries, he said. One of the men who was buried under rubble remained in critical condition.

Two neighboring buildings were evacuated as city inspectors examined their stability and tried to determine the cause of the collapse.

The Brooklyn Department of Buildings commissioner, Susan Hinkson, said the building owner had a permit for the work, but had been issued several violations.

“We don’t know the condition that it was in right before the collapse,” she said. “That will take a while to determine.”

The building was reduced to a pile of rubble shrouded by a torn blue tarpaulin. A man identified by city officials as the building’s owner stood talking nearby with several companions, but declined to comment to reporters on the collapse.

David Allaband, who lives across the street, said he had been reading in his apartment when he heard a loud rumble.

“I thought it was a low-flying jet,” he said. “I came out and it was all down.”