An explosion in the hull of a Navy cruiser during routine maintenance injured six workers on Saturday, one of them critically, authorities said.
Subcontractors from the National Steel and Shipbuilding Co. were working in the fuel tank of the USS Lake Champlain as it sat in dry dock when the explosion occurred just after noon, said San Diego Fire Department spokesman Maurice Luque.
"Apparently it was caused by flammable gas that ignited," Luque said. "We don't know how or why."
Four of the workers were taken to UC San Diego Medical Center.
One remained in critical condition with potentially fatal burns late Saturday, said Denise Thompson, a nursing supervisor at the hospital.
Another was in fair condition and two were in good condition, she said.
Two other workers were treated at the scene of the explosion and released, Luque said.