SHELTON, Conn. (AP) – A fatal trench collapse on Saturday buried a mason beneath 11 feet of earth and rock.

It took rescuers nearly four hours to recover the body of Ademilson Vieira, the Connecticut Post reported.

Rescue workers and Michael Ullrich, Shelton’s assistant fire chief, believe Vieira, of Bridgeport, may have been fatally crushed by falling stones and excavated dirt or he may have suffocated.

Ullrich said there was no shoring behind the trench Vieira was digging for a retaining wall behind a house. Shoring typically consists of plywood bracing to stabilize a construction site by preventing the collapse of excavated material.

“It is very odd that this construction site did not have any shoring,” Ullrich said. “That is not the customary practice.”

U.S. Occupational Safety and Health Administration officials were investigating.

Vieira’s co-workers called 911 to report the accident and initially clawed at the dirt and stone for 20 minutes to free him.

The Medical Examiner’s Office will conduct an autopsy to determine the cause of death.

Vieira was employed by Edward Osello Masonry of Monroe.