The first mustard gas leak in three years was confirmed Tuesday at a chemical weapons stockpile in Kentucky, less than a month after workers there found a leak inside a separate storage igloo housing a deadly nerve agent.

But officials said the latest leak poses no danger to the community nor the surrounding atmosphere.

Richard Sloan, public affairs officer for the chemical storage site at Blue Grass Army Depot in Richmond, said trace amounts of mustard gas vapor were detected during a routine inspection of a storage area this week. Army workers won't know whether there is also a liquid leak until a closer inspection inside the igloo.

Because the igloo is full of artillery weapons containing mustard agent, the biggest chore in cleanup efforts is to pinpoint which one is leaking, he said.

"If they could walk in there and find a puddle, that would be wonderful, but that's probably not going to happen," Sloan said. "What they're probably going to do is find several thousand projectiles and no way of telling which one of those had let a little vapor through."

Another concern is the summer heat, which could raise the temperature inside the opened igloo and heighten the chances of additional leaks. Once the leak or leaks are identified, the 155-millimeter projectiles that are affected will be stored in packed containers to limit the risk of future leakage.

Mustard agent is among the least lethal of the Cold War-era weapons set to be destroyed at storage sites in Kentucky and elsewhere by 2017 to comply with an international treaty. The agent causes a debilitating but usually nonfatal outbreak of severe blisters over the body of anyone coming in contact with the chemical. It often requires immediate medical attention.

Earlier this month, the depot announced it had detected a second vapor leak in less than a year of sarin, a far deadlier weapon housed in the storage igloos. While the sarin leaks were contained, including a more serious one last August, the Army is planning to use a mobile destruction unit to dispose of the sarin canisters by year's end.

Craig Williams, executive director of the Kentucky-based watchdog Chemical Weapons Working Group, was highly critical of the Army for its handling of the first sarin leak, particularly what he called a lack of immediate information released to the public. But he said Tuesday that proper procedures have been followed after subsequent leaks, including the one this week.

"The diligence shown out there in finding these things really boosts my confidence more than it does worry me about the consequences," Williams said.

He added, "In the bigger picture, the only way to eliminate risks associated with all this stuff is to eliminate the weapons themselves."

The timetable for destroying the chemical weapons has been a moving target. But Williams said the current 2017 deadline may be met if the Pentagon provides sufficient funding for the effort. The Kentucky site is to use a chemical neutralization procedure to destroy its 523 tons of agent, including mustard gas and the nerve agents GB and VX.