I've heard 3, 11, none, and unknown.
So it's unknown.
Unsourced information is unreliable. Neither of you links a source. Anyone care to do it right?
Also, the "too soon" comment... Honestly. If DF had existed in 2001, do you think we wouldn't have discussed the WTC attacks on these forums? Naive methinks... I may be against discussion of poop\feces on these forums, but since we play games which simulate real-life environmental and construction catastrophes, it seems to make sense to discuss those here when they happen in real life.
Death is a reality, it is the truly coy and skittish who give it unnatural power by treating it with undue reverence and excuse it from the same scrutiny to which everything else in our world is subject\victim. Death interests us all, how we die, why we die, when we die, videos of dying, headlines of who's died recently. Because it looms at the end of life, ostensibly inevitable, we all find its study and circumstance to be very interesting, each in our own way. If a chasm into the underworld opened beneath your apartment and you disappeared from your city all of a sudden... Chances are you'd be dead. But you'd have died one of the more... shall we say, "stunt-worthy" deaths. Compared to going in your sleep of old age... Which doesn't get you quite the same type of impressive headstone.
So did anyone die in that collapse or no? Lucky on them if they didn't. Extra lucky if they were inside and managed to survive tumbling into the underworld. :O For those who aren't aware, nearly all of south america is crisscrossed by caverns carved out by surface water. A sinkhole exactly like that one opened in Guatemala about half a decade ago, and the picture was entirely similar (with no bottom visible). How deep do these things go? You can't just...cover it up, either. Does it become a permanent opening in that city? Do people go rappelling down it? Do they build a bridge? Evacuate 3 city blocks? All interesting stuff.