Digging began Thursday to discover whether additional areas at Defense Depot Ogden have been contaminated with deadly mustard agent.

The excavations will take place in the vicinity of the Ogden base where 100 vials of mustard agent were dug up in 1988, during an initial investigation of environmental problems. Del Fredde, environmental protection coordinator for the depot, said the agent, which can create poison gas, was used in past training exercises."Further field investigation and sample analysis show that there may be other burial sites in the area," Fredde said. The region is in the southwestern part of the depot.

The new investigations should last about two weeks. Safety precautions will be taken to protect workers at the site, depot employees and the surrounding community, he said.