Cologne Archive Catastrophe Were Subway Builders Cautious Enough?

Many in Germany's fourth biggest city are asking if the collapse of one of Europe's most important historical archives was caused by the construction of an underground railway line. One report suggests work on the line wasn't done as carefully as it should have been.
Reported by Matthias Bartsch, Andrea Brandt, Guido Kleinhubbert and Mathias Schreiber.