The Army continues to detect mustard agent in a building in the Edgewood area of Aberdeen Proving Ground where a leak of the deadly chemical was reported Wednesday morning, George Mercer, chief spokesman at Aberdeen Proving Ground, said yesterday. None of the agent has been detected outside, he said.

An Army team that entered the building late Wednesday evening did not find the leak during its inspection. Officials were planning yesterday to search more thoroughly.

"Finding the leak may be difficult because it could be as small as a pinhole," Mercer said. "There were no puddles on the floor."

APG's Edgewood storage yard holds 1,400 containers of mustard agent, said Mercer, who provided a revised figure yesterday. Mercer said the containers hold varying amounts of agent. Details on the condition and size of the containers are secret.

Mustard agent is a blistering agent that affects the skin, eyes and respiratory tract. The chemical is thought to have been last used in wartime in the 1980s, when Iran alleged that Iraq had used it in the war between the two nations.

"The real issue now," said Mercer, "is finding the leak and evaluating what to do with the container."