NOW THIS REALLY, REALLY ROTS

We can't find Saddam's WMDs...but they apparently can. And now they are trying to use them against us.

A roadside bomb containing sarin nerve agent recently exploded near a U.S. military convoy, the U.S. military said Monday.

Bush administration officials told Fox News that mustard gas was also recently discovered....

"The Iraqi Survey Group confirmed today that a 155-millimeter artillery round containing sarin nerve agent had been found," Brig. Gen. Mark Kimmitt (search), the chief military spokesman in Iraq, told reporters in Baghdad. "The round had been rigged as an IED (improvised explosive device) which was discovered by a U.S. force convoy."

The round detonated before it would be rendered inoperable, Kimmitt said, which caused a "very small dispersal of agent."

A senior Bush administration official told Fox News that the sarin gas shell is the second chemical weapon discovered recently.

Two weeks ago, U.S. military units discovered mustard gas that was used as part of an IED. Tests conducted by the Iraqi Survey Group (search) and others concluded the mustard gas was "stored improperly," which made the gas "ineffective."

They believe the mustard gas shell may have been one of 550 for which former Iraqi President Saddam Hussein failed to account when he made his weapons declaration shortly before Operation Iraqi Freedom began last year.

Investigators are trying to determine how insurgents obtained these weapons — whether they were looted or supplied...

Gazi George, a former Iraqi nuclear scientist under Saddam's regime, told Fox News that he believes many similar weapons stockpiled by the former regime were either buried underground or transported to Syria...

George said the finding likely will just be the first in a series of discoveries of such weapons.

"Saddam is the type who will not store those materials in a military warehouse. He's gonna store them either underground, or, as I said, lots of them have gone west to Syria and are being brought back with the insurgencies," George told Fox News. "It is difficult to look in areas that are not obvious to the military's eyes.

"I'm sure they're going to find more once time passes," he continued, saying one year is not enough for the survey group or the military to find the weapons."