this agent. the organization for the prohibition of chemical weapons said this particular chemical used on the schiphols back in march was a very high purity and also persistent. meaning it doesn't just evaporate like a sarin gas in a matter of hours or days. other chemical weapons experts we've spoken to say it can remain viable for months potentially. and only a couple of drops can be deadly. now, as to how these two may have been contaminated, lots of theories floating around. nothing officially from police. but one thought is that they were exposed somewhere in the town of salisbury when they were there the day or maybe in the hours before they fell ill, then went home, and that's where the symptoms kicked in. there are a couple of locations in salisbury where police are searching today. >> and i'm sure a lot of nervous people if, indeed, that's what's happening, is there's some