The statement by the US military spokesman in Iraq that an improvised bomb made up of a shell containing nerve agent was discovered by an American convoy raises some disturbing questions.
The Americans say that a 155mm artillery shell containing two constituents of sarin was used by insurgents in Iraq as part of an improvised explosive device.
US troops face the possibility that Iraqi chemical weapons still exist
The weapon was a binary shell, which contains two chemicals that only mix to form the nerve agent once the warhead is in flight after being fired.
In this case, the use of the shell as a roadside bomb meant that the chemicals did not mix and its partial detonation only resulted in some minor contamination of US personnel.
But if this shell is what it seems - a filled chemical munition - where did it come from? And how many more shells might there be?
Iraq was supposed to have destroyed all such munitions under United Nations supervision in the wake of the 1991 Gulf War.
Iraq had large stocks of 155mm shells containing mustard gas.
But it claimed only to have filled a small number of such shells with binary nerve agent as an experimental project, which the Iraqis said, never entered full-scale production.
Nobody knows how many such shells were manufactured or how many may exist today.
These shells could be over a decade old and the chemicals they contain could have degraded.
But looked at more broadly, is this the first sign, as the US and British governments claimed, that Iraq really did have chemical weapons?
One shell clearly does not make a chemical arsenal.
But if Iraqi insurgents knew where to find this one, there is the disturbing possibility for the US-led coalition that other similar munitions may have fallen into their hands.