Discreet (Exit Only) Underground tunnels were made to ensure that no one was seen leaving Combi's lab. This precaution was made to stay under the radar if they were being watched by enemy cartels. The tunnels bled into both the deep outskirts and deep into Mexico city.
The exits of these tunnels could not be opened from the outside unless they were drilled into. The latches were 5inch thick metal sheets that locked into the ground once they closed but can be opened through one side. Outskirt exits were for emergency purposes, but their access was only for Combi and his selective group. The entrances to the Outskirt exit tunnels were blocked by Combi's quarters, as to which he has the keys.
The inner city tunnels that led into Mexico City's alley ways were for Combi's drug mules to enter through his lab and exit through those tunnels to sell their product. The inner city tunnels were also exit only.
The tunnels are twenty feet underground.
Subject: Combi's Lab (Underground Tunnels) (Underground Level)