I created 4 beacon pyramids right next to each other in creative. Then I switched my gamemode to survival and removed the beacon block. The beacon beam did not disappear. I then removed several of the pyramid blocks and the beacon beam still did not disappear.

The beacon with 4 layers has an unconsumed iron ingot sitting in its interface. The rest of the beacons do not have any ignots/gems sitting inside them.

Attached is a screen shot.

Upon reloading the world, the beacon beam is gone and the iron ingot in the 4 layer pyramid beacon is gone.