Originally posted by: Vaerilis
They had biohazard signs on them and the people opening the container checked the canisters for leaking in gas masks, so I guess that they are some kind of viral weapons or plain nerve gas.
The terrorist with the yellow tie had a few minutes to get away, so he might be in building adjacent to the airport instead of being in the airport's basement. (it didn't really make sense to me, either). It's also possible that they've smuggled the concrete container into the airport basement and it was sitting in there for some time before the attack.