fires hampered that. we know water hampered that. they found areas they're able to go to, lift up concrete, and put search cameras in there, try to get hearing and visuals back, use the canine to see if you can get more feedback from any victims. >> you teach this practice. i will get into the equipment and process, but i want to ask about the fire. officials have acknowledged they don't know the source of the fire. >> correct. >> what challenge does that represent for people that are in the midst of it? >> always presents a challenge. good thing, the smoke is lighter, it tends to drift to the top. rescue crews have used a trench to gain access. it is always a concern, could have been one of the vehicles underneath in the parking garage, anything under that