Why did the twin towers collapse?

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Tags

1. #fires
2. #manual
3. #impact
4. #stories
5. #primarily
6. #water
7. #firefighting
8. #multiple
9. #towers
10. #actual
11. #sprinklers
12. #caused
13. #other
14. #continued
15. #debris
16. #collapse
17. #preliminary
18. #ignited
19. #unabated
20. #findings
21. #damage