The word of the collapse in the secretive nation's capital was reported Sunday morning by the North's official Korean Central News Agency, which gave no death toll but said that the accident was "serious" and upset North Korea's leader, Kim Jong Un.
The report said it occurred in the capital's Phyongchon district on Tuesday "as the construction of an apartment house was not done properly and officials supervised and controlled it in an irresponsible manner."
That could mean the casualties could be in the hundreds because a typical North Korean family has four members.
However, it was not clear that all the residents were inside at the time of the collapse, or that four people lived in each apartment.
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It is not unusual for people to start living in apartments before the construction is complete. The official said he did not have any figure for the actual death toll.
On the streets of Pyongyang today, residents expressed outrage over the incident.
"This accident happened because they broke the rules and methods of construction," resident Pak Chol told The Associated Press.
"After this accident, we must make sure that this kind of terrible accident never happens again, by sticking to the proper method of building."
Another resident, Hong Nam Hyok, said that "everyone in Pyongyang is now sharing the sorrow of the victims and the bereaved families."
The KCNA report cited one official as saying Kim Jong Un "sat up all night, feeling painful after being told about the accident."