Growing potatoes in bin bags

I've planted a few potatoes in bin bags a few weeks ago, covered with soil and watered them.
I know you're supposed to keep covering them up by adding more soil as they grow.

They've not got some green sprouts coming through the soil.  Do I cover these green sprouts to bury the potatoes fully, or do I wait longer and allow these green bits access to light?

Thanks!

And if its a bin bag, don't try to move it!  soil is very heavy and the bag would split!

Yes they will rot, but once the shoots are showing the seed spud is effectively gone anyway. Anything in pots and bags needs loads of water especially in this weather.

Providing you have remembered drainage holes as far as I'm concerned once the plants are filling the bag and are showing lots of top growth they can't have enough water. You may also want to feed them at that point as the soil / compost you have used will be somewhat lacking in nutrients.