WALNUT CREEK, Calif. (AP) – A construction worker who was burned when an underground fuel pipeline exploded has died, the third confirmed fatality from the fiery accident.

A construction crew struck the petroleum pipeline Tuesday, sparking an explosion and fire that burned several nearby buildings and shot flames high in the air.

Two additional workers were missing and presumed dead and four others remained hospitalized with moderate to severe burns.

The missing workers are believed to be trapped inside a 15-foot-wide water pipe they were welding when the line was hit, said Steve Maiero, a spokesman for the Contra Costa Fire Prevention District.

Firefighters had hoped to enter the ditch on Wednesday, but after residual fuel and vapors from the severed pipeline reignited at least twice, authorities determined it wasn’t safe and postponed the recovery effort until Thursday.

The ruptured pipe is owned and operated by Houston-based Kinder Morgan Energy Partners and carries gasoline, diesel and jet fuel from Concord to San Jose.

Kinder Morgan employees were at the site Wednesday trying to cap the line and to drain any remaining fuel, said Brad Rovanpera, a spokesman for the City of Walnut Creek.

All of the victims were thought to have been members of the crew working on a water pipe replacement project for the East Bay Municipal Utility District.

The construction work was being done by Mountain Cascade of Livermore, said Charles Hardy, a spokesman for the utility district. It was unclear whether the victims were Mountain Cascade employees or subcontractors, he said.