The U.S. Coast Guard was attempting to find two old weapons dumped back into the Atlantic Ocean by the ESS Pursuit some 45 miles south of Long Island, N.Y., said Coast Guard Petty Officer James Rhodes. He said locating the munitions would be complicated.

The two munitions measured about 12 inches in length and three inches in diameter and were brought on board the ESS Pursuit with some clams. Coast Guard officials think one of the munitions was damaged, allowing its contents to leak.

The Atlantic City-based fishing crew was trawling waters Sunday that were known to have been the site of weapons dumping decades ago. The dumping zone declaration, however, is just a cautionary advisory and does not bar fishermen from the waters, Rhodes said.

The fishing boat docked Monday in New Bedford, Mass., when crew member Konstantin Burndshov began to have trouble breathing and developed skin blisters. A few hours later, a second crewman was brought back to land when he said he felt ill. Two more fishermen were dropped ashore later in the day with one crew member saying his eyes and nose were irritated.

The toxicologist providing treatment to Burndshov, Edward Boyer, said the severe blisters and other symptoms indicated the crewman had been contaminated by mustard gas. That diagnosis was verified by testing. He was recovering well from his injuries, the doctor said.

The protective gear Burndshov wore on the boat -- long gloves and oil skins -- was not enough to keep the blister agent from reaching his body, Boyer said. "It literally pulls the top of the skin off the layer underneath it," he said.

Mustard agent was used most notably during World War I and occasionally afterward. It can be lethal if breathed in as an aerosol.

From the end of World War II through 1970, the U.S. Defense Department disposed of some conventional and chemical weapons by tossing them into offshore waters. Congress outlawed all munitions dumping in the seas in 1972. Patchy record-keeping has made it extremely difficult to figure out decisively what quantities and what kinds of munitions were disposed of in the oceans.

A U.S. Army analysis in 2001 identified 74 cases of munitions dumping 42 in foreign offshore waters and 32 in domestic coastal waters. In one instance in 1967, the military offloaded more than 4,500 blister agent-filled bulk containers and 7,380 munitions filled with sarin nerve agent into waters off the New Jersey coast.

A fisherman suffered mustard exposure in 1976 near Hawaii while a shell carrying the blister agent turned up six years ago in clamshell material used for a driveway in Delaware after being hauled up close to New Jersey.

Chemical weapons expert Steve Bird said mustard agent could remain dangerous for an extended period even as it begins to deteriorate.

"The stuff still works just the same, and is still as toxic as it was before," Bird said.

While aging, submerged munitions are a threat to the fishing crews, experts do not think they are likely to be used by terrorists in an attack.

"If I'm a terrorist and I want to use chemical weapons, I can go to 16 hardware stores and get the stuff I need to make it, rather than be trolling around in the middle of the ocean," said Craig Williams, who heads the Kentucky-based Chemical Weapons Working Group.

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