WASHINGTON – The U.S. Army Corps of Engineers has uncovered what could be a fourth major disposal area for World War I-era munitions and chemical weapons in the nation's capital.

Digging was suspended April 8 as a precaution at the site in the pricey Spring Valley neighborhood near American University after workers pulled smoking glassware from the pit, project manager Dan Noble said Thursday.

Preliminary tests show the glassware was contaminated with the toxic chemical arsenic trichloride. Officials will review safety procedures before
digging continues.

Workers also discovered a jar about three-quarters full of a dark liquid that turned out to be the chemical agent mustard. It was used during World War I as a weapon
that caused blisters, breathing problems and vomiting.

"It's a much larger disposal area than we predicted," Noble said. "The nature of debris is so different, perhaps it's a different disposal area."

It's too soon to know for sure, Noble said.

During World War I, the Army used the university as an experiment station to develop and test chemical weapons. Previously, there were three known
sites where weapons and chemicals were buried.

Glassware, chemicals, contaminated soil and munitions have been found since January in the front yard of a home next door to the university president's house, the Army Corps has revealed. About 30 intact items were sent to an Army lab in Edgewood, Md., for testing, Noble said.

American University spokeswoman Camille Lepre said there were no plans to move or cancel any campus events scheduled at the president's house.

About 350 pounds of glassware and debris had been removed from the site, along with about 676 barrels of soil, according to a campus memo
Wednesday by university president Neil Kerwin.

This is the first discovery of the smoking chemical arsenic trichloride in the cleanup project. It can be used to develop the blistering agent
lewisite, Noble said. An Army Corps spokeswoman said the chemical was
contained and was not exposed to the outside air.

Several munitions also were discovered in recent months, including a 75 mm shell that was half full with a tear gas agent, Noble said. A few
munitions also have been uncovered in the yards of homes that fall
within a firing range near the campus, he said.

The Army Corps is preparing to destroy some munitions at a secured facility nearby as soon as Friday.

Last year, the Army Corps believed it had cleared the disposal area known as "Pit 3" but continued to dig test pits.

The latest discoveries came as a surprise to residents who worry the Army Corps is trying to end its cleanup before all munitions are uncovered.

"I'm concerned there's a rush to make the decision to get out," said Nan Wells, a neighborhood commissioner who represents area residents.
"Things have been downplayed. That doesn't mean that I don't think the
Army can handle this successfully."

This is the fourth major dig for munitions and toxic agents over the past 16 years since the burial pits were discovered in the neighborhood of
multimillion-dollar homes. The current excavation began in 2007 at the
house, which is owned by the federal government and located next to the
South Korean ambassador's residence.

The cleanup project is one of the only places in a major city classified by the Army Corps as a "Formerly Used Defense Site."