air passages from the surface down to the cave system. the difficults say experts is even if they find one might lead to a different system. the cans of it hitting the boys exactly is relatively slim. but obviously pulling them up through a chamber of some kind would be advisable. the divers i have seen here are all technical divers using years and years of experience. it's extremely dangerous and difficult to get the kids out if they have to come through the water. >> still a long way to go. david live for us in thailand. thank you. to the uk now. police say a couple in southern england was exposed to the same military grade nerve agent used against a former russian spy and his daughter in march. now investigators are trying to determine if the two raises are somehow connected. erin mclaughlinen lives from amesbury, green. such a mystery and people must be really concerned. >> reporter: extremely concerned, christine.