What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED DUE TO: GOT THE CABIN ALTITUDE WARNING ABOUT 10,000 MSL; WE DEPLOYED THE O2 MASK. AIRCRAFT AIR INTERRUPTED BACK TO AND LANDED SAFELY AT MEX. OUTFLOW VALVE AND PRESURIZATION CONTROL OPERTIONAL CHECK GOOD, PER AMM21-31-00-710-801. AND ACCOMPLISHED OUTFLOW VALVE VISUAL CHECK, PER AMM 21-31-03-400-801. NO FAULT NOTED OR FOUND AT MOMENT.