Is this a septic tank problem?

I rent a house with a septic tank, and in my back yard, around the area where i think the tank is burried, a just noticed a hole in the ground. Its about 2 feet wide, and 6 feet deep. When i peered inside, i noticed towards the bottom of the hole, the wall of it appears to be lined with cinder blocks.. is this a septic tank issue? do they line the trench with cinder blocks before they put the tank in? so far my plumbing hasnt been acting up, and im about to call the landlord.