Speaking outside Scotland Yard, Commander Stuart Cundy added: "I have investigated major crime for most of my service and I have seen some terrible things. But I don't think anything prepared me for what I was going to see when I was in there."
"It's hard to describe my feelings, because I cannot imagine, and I would not want to put myself in the position of those families who have lost their loved ones.
"But being with colleagues from the London Fire Brigade when I was in there, colleagues from the London Ambulance Service and other police officers, I think it's fair to say it is incredibly emotional working in there.
"But we will do it with our utmost professionalism and we will do everything we can as quickly as we can to locate everybody who is in there."