I heard a news report that they (the British Military) were looking for Uranium deposits. The trouble is they never told the Mexican Government.
The mystery is heightened by the fact that they have turned down all the assistance the Mexican authorities have offered, and are willing to wait a week or more till British rescuers arrive.
Trapped by heavy rain, one British rescuer said it might be a full week before they are all out safely. They must have gone in very well prepared for what was mean't to be a 36 hour expedition.