Mario Moreno planned originally to borrow some trucks and equipment from Mexico City's fire department, but was dissapointed when noticed that all the equipment, trucks snd even the buildings were a total disaster. In fact, due the lack of equipment, the firefighters could hardly work. All the mess was (obviously) product of the corruption of the authorities. So, Mario bought brand new equipment, trucks and even rebuilt a whole building in order to have the set ready for the film. No need to say that he donated everything to the city afterwards.