WASHINGTON -- You simply can't safely bomb a chemical weapon storehouse into oblivion, experts say. That's why they say the United States is probably targeting something other than Syria's nerve agents.
But now there is concern that bombing other sites could accidentally release dangerous chemical weapons that the U.S. military didn't know were there because they've lost track of some of the suspected nerve agents.
Bombing stockpiles of chemical weapons -- purposely or accidentally -- would likely kill nearby civilians in an accidental nerve agent release, create a long-lasting environmental catastrophe or both, five experts told The Associated Press. That's because under ideal conditions -- and conditions wouldn't be ideal in Syria -- explosives would leave at least 20 to 30 percent of the poison in lethal form.
"If you drop a conventional munition on a storage facility containing unknown chemical agents -- and we don't know exactly what is where in the Syrian arsenal -- some of those agents will be neutralized and some will be spread," said Daryl Kimball, executive director of the Arms Control Association, a nonprofit that focuses on all types of weaponry. "You are not going to destroy all of them."
"It's a classic case of the cure being worse than the disease," Kimball said. He said some of the suspected storage sites are in or near major Syrian cities like Damascus, Homs and Hama. Those cities have a combined population of well over 2 million people.
When asked if there is any way to ensure complete destruction of the nerve agents without going in with soldiers, seizing the chemicals and burning them in a special processing plant, Ralf Trapp, a French chemical weapons consultant and longtime expert in the field, said simply: "Not really."
Trapp said to incinerate the chemicals properly, temperatures have to get as hot as 2,100 degrees Fahrenheit. Experts also say weather factors -- especially wind and heat -- even time of day, what chemicals are stored, how much of it is around and how strong the building is all are factors in what kind of inadvertent damage could come from a bombing.
There is one precedent for bombing a chemical weapons storehouse. In 1991, during the first Persian Gulf War, the U.S. bombed Bunker 13 in Al Muthanna, Iraq. Officials figured it contained 2,500 artillery rockets filled with sarin, the same nerve gas suspected in Syria. More than two decades later the site is so contaminated no one goes near it even now.
That bunker is a special problem for inspectors because "an entry into the bunker would expose personnel to explosive, chemical and physical hazards," says a 2012 report by the Organisation for the Prohibition of Chemical Weapons, which implements the international chemical weapons convention.
Pentagon planners are also worried about accidentally triggering a nerve agent attack by hitting weapons stores that have been moved by the government to new locations.
Over the past six months, with shifting front lines and sketchy satellite and human intelligence coming out of Syria, the U.S. intelligence community has lost track of who controls some of the government's chemical weapons supplies, according to one senior U.S. intelligence official and three other U.S. officials briefed on the information presented by the White House as reason to strike Syria's military complex. They spoke on condition of anonymity because they were not authorized to discuss the briefings publicly.
That's a very real risk, said Susannah Sirkin, international policy director for the Physicians for Human Rights, which has been monitoring weapons of mass destruction for more than two decades.
"You would risk dispersing agents into the environment," she said. "Given that sarin is not seen or smelled, that's terror."
Another issue is that by bombing storage sites that are near contested areas in the civil war, the chemical weapons can fall into others' hands, including extremist rebels or pro-Assad militia, Kimball said.
"What we're looking at in Syria is an unprecedented situation," Kimball said.
-- AP Intelligence Writer Kimberly Dozier contributed to this report.