If the building is built on a cement slab (most strip mall and factories are), then all electrical and gas must be ran above ground. If a machine or implement requires gas and it is located in the center of the building, then it will require a gas line to be ran overhead.

In my area we have natural gas, but rural areas around me have propane. Not sure what is the fuel of choice where this happened.

I previously worked in the propane industry doing safety inspections. I currently work in the manufacturing industry as a Environmental Health and Safety dude. Gas lines are not inspected as often as I think they should.