RICHMOND — A low-level leak of mustard agent was detected in a storage igloo, and unfiltered process water used to wash explosives out old conventional munitions made its way to the Blue Grass Army Depot’s general waste-water treatment plant.

Depot officials reported both incidents Monday, saying they believe no toxins were released into the general environment. Local and state environmental immediately were notified, they said.

A mobile monitoring lab detected low levels of mustard agent vapor in a chemical weapons igloo containing 155-mm projectiles Monday morning, according to Sheryl Lowell, spokesperson for the chemical weapons activity at the depot.

“The extremely low level of mustard agent vapor in the interior atmosphere of the igloo was discovered during routine weekly monitoring,” she said. “The leak poses no danger or risk to the citizens of Madison or surrounding counties.”

A Boston College chemistry student was injured when a beaker exploded during an experiment this morning, cutting her face and forcing the evacuation of Merkert Chemistry Center, officials said.

The student was working alone in the lab with a small amount of thionyl chloride -- a substance commonly used in organic chemistry experiments -- when it reacted violently, according to fire department spokesman Steve MacDonald.

The student, Hee Yeon Cho, received cuts on her face and minor burns on her hands, he said.

Boston College spokesman Jack Dunn said Cho, who recently finished her fourth year in the doctoral program, subsequently left the lab to take care of the cuts while fellow graduate students notified Boston College police. The university then notified the Boston fire department.

“This was a minor chemical reaction that caused the beaker she was using to break,” Dunn said.

Fire crews and a hazmat team responded to a call at 10:47 a.m., but cleared the scene by 1 p.m., MacDonald said. Throughout the early afternoon, some responders’ vehicles remained at the lab at 2609 Beacon St. in Brighton, but people were allowed in and out of the building.

After going through a series of showers in a mobile decontamination unit, Cho was taken to St. Elizabeth’s Medical Center, where she was treated for injuries that do not appear life-threatening, MacDonald said. No one else was injured, Dunn said.

After the beaker ruptured, Cho put a paper towel over the cut on her cheek and then drove herself home, said Chris Schuster, 25, a graduate chemistry student at the scene.

Her return home complicated the cleanup effort: Crews also had to decontaminate her car and her apartment in Brighton, MacDonald said.

“It was more challenging because the student left,” he said.

A chemistry professor came to the lab and determined responders should dilute the thionyl chloride with “large amounts of water,” MacDonald said, and Boston College brought in a cleaning company.

It is still unclear what caused the reaction, he said.

Thionyl chloride reacts strongly with moisture and can be dangerous to humans if vapors are inhaled, said Lawrence Scott, Cho’s professor. The chemical can be used to make mustard gas and nerve toxins.

“Honestly, I think she was probably never expecting this to happen. This seems like a somewhat standard procedure,” Schuster said regarding the experiment.

Schuster said chemistry students at Boston College are required to take a lab safety training course. While it is uncommon for students to work alone, the department’s guidelines for lab safety do not forbid it, according to a document posted online by the Boston College Office of Environmental Health and Safety.

Still, researchers are warned not to work with hazardous or potentially explosive compounds by themselves, said Kai Hong, 26, another chemistry graduate student who was going to the building this afternoon.

Dunn said that to his knowledge, Cho, whom he called a “skilled researcher,” did not violate any safety procedures.

NEW BEDFORD — The fisherman who was blistered and hospitalized after dredging up a chemical catch suffered from rare mustard gas exposure, according to Edward Boyer, chief of the division of medical toxicology at the UMass Memorial Medical Center in Worcester.

UMass Medical Center sent blood and urine samples to a state laboratory in Boston, which made the confirmation, said Boyer, who is also a professor of emergency medicine at UMass Medical School.

"There have been five exposures to mustard gas in the United States that we know of since World War I ... that have been published in the literature," he said Tuesday.

NEW BEDFORD — Four fishermen were taken to the hospital Monday after appearing to have dredged up some dangerous chemicals while they were fishing off Long Island.

The chemical is believed to be some kind of "nerve agent, so that's leading people to speculate that it's a possibility of mustard gas," New Bedford Fire Chief Brian Faria said at a news conference Monday afternoon.

The fishermen were aboard the ESS Pursuit, which was dredging for clams when the crews pulled up canisters from the sea. The Coast Guard, the New Bedford Fire Department and a man who was aboard the ship all gave different accounts of how many canisters were pulled up, although Faria said he believes they dated back to World War I.

Kevin O'Sullivan, 33, of New Bedford was one of the fisherman on the ship and described the canisters as about 1 foot by 3 inches, resembling a large bullet.

Dredging up these types of curiosities "happens all the time," he said, adding that the canisters were thrown overboard.

Jeff Hall, a spokesman for the Coast Guard, echoed him, saying, "There's places all over the country where they've dumped munitions in the past." And in April, another clam boat brought in a haul of active, World War I-era grenades to the Wright Street shellfish plant.

However, a fellow crewmember — whom O'Sullivan knew simply as "Kosta" — later said he'd noticed one of the canisters was "leaking or cracked."

Kosta eventually began to blister, according to O'Sullivan, who said the man had one blister measuring approximately 4 inches by 2 inches on his forearm and a second on his leg.