After World War II, the U.S military dumped 2,558 tons of lethal chemical agents — including mustard, cyanide, lewisite, cyanogens and chloride weapons — at three deep-water sites off O'ahu, according to a 2007 report to Congress.

But locating precisely where those chemicals landed on the vast sea floor is like finding the proverbial needle in a haystack.

Last month, following years of public concern, the University of Hawai'i's School of Ocean Earth Science and Technology, under contract with the military, completed the first part of a pioneering effort to locate some of those chemical munitions at one site 3 to 6 miles south of Pearl Harbor.

While neither the researchers nor the military believes they found the mother lode of chemical weapons, both agree the UH team's method of using remote sensing equipment in conjunction with the two UH research submersibles, Pisces IV and V, can lead to finding the vast tons of chemical weapons that have littered the sea bottom for more than six decades.

"The information we have on the disposal itself was sketchy, vague," said J.C. King of the Office of the Deputy Assistant Secretary of the Army for the Environment, Safety and Occupational Health.

"But the ability to be able to use sonar to locate munitions and understand what you are seeing, and then to dive to those sites and match up what's actually on the bottom with what they are seeing on the sonar — that's going to help us a lot as we try to find the ... disposed chemical munitions," King said.

King, who went on three of the submersible dives, said that what he saw between 900 and 1,600 feet below sea level was either conventional weapons or multi-purpose weapons — meaning bombs that could be either conventional or chemical.

In 2007, the UH research team, headed by Margo Edwards, used high-resolution sidescan sonar and remotely operated underwater vehicles to map and track what appeared to be long trails of disposed munitions in a 45-square-mile area.

Then last month, the school's pair of three-person submersibles were able to locate munitions and take water and sediment samples in areas around the bombs.

"Nobody's really ever done this before," said Edwards, who said the operation was successful in finding munitions dumped at sea. "We went to all the places that in the sonar data looked like munitions and, lo and behold, they did turn out to be munitions."

In slightly less than two weeks of dives, the submersibles found and collected samples from 1,000 to 2,000 discarded munitions, Edwards said.

"If I'd sent the submarine down without the sound information, the chances of me running into a munition would be pretty low in a 70-square-kilometer area," she said.

The goal was to devise a method of finding the munitions and testing area samples to discern how the weapons are affecting the environment and how the environment is affecting the weapons, to make an informed decision about how best to deal with the problem, she said.

William Aila, a Wai'anae Coast resident who has actively followed the dumped chemical weapons issue, said that while the new research is encouraging, it's incomplete.

"They haven't found the mother lode," Aila said. "They still need to do that. That's important, because you're going to have a higher concentration of all of these chemicals where that mother lode is."