From reading the article closely, I believe what happened is that the bodies and lots of debris collapsed into the basement area. That much compacted debris would still be very hot and smoldering in some places and soaked with water in others, with possible live wires or exposed gas lines as first responders got there. These conditions would prevent them from being able to excavate, or even see, any bodies, at least for the first day and a half, if not more. It would require painstaking forensic sifting after it became safe enough to approach. Until a positive ID from bone fragments or DNA, an announcement could not be made by officials, although it looks like family members have made the logical assumption and they told the school and their friends.
“I believe what happened is that the bodies and lots of debris collapsed into the basement area.”
Yes, I was thinking about that too. And you are right, the authorities would not make any speculative remarks about loss of life. Which is good, they shouldn’t.