Moggie
Highly improbable that the troops would even be looking for WMD at this stage, they are more concerned with their principle task. Looking for WMD in the more remote parts of Iraq which have yet to be secured would be highly dangerous and time consuming, particularly whilst the irregulars are known to be embedded with the locals and possibly very hostile. Plenty of time to go looking when they have manpower to spare and they can be properly protected.
Of course it is possible that they may stumble on some but only if they happen to be in their intended path to their main objective.