Videos shared on Facebook show white balloons drifting towards mourners. The videos were widely reported in the tabloid media earlier this year.
The first video shows a balloon move a short distance, and then stop at one mourner.
The second video shows a balloon floating towards another mourner, stopping briefly as the string hooks onto the chair, then proceeding.
(The top image is a partial panorama made from this video)
What is happening here is that the balloon are simply moving with the currents of the air in the room. There's an AC unit at one end of the room which is probably blowing air out, and taking it it. This creates slowly circulating air in the room.
So why the claims of ghosts? Well there's a number of questions that make people suspicious. I'll try to answer them.
Q: Why are the balloons moving one at a time, if the air is moving why don't they all move?
A: Because the air currents in the room are very slow. The balloon will only move with them if it is not touching anything. This means it needs to be neutrally buoyant (so it does not rise to the ceiling or sink too quickly to the floor), and it needs to not be touching a wall (where friction and static cling will stop it).
There are a lot of balloons and the mourners have been there for days. The balloons are are slowly losing helium, and will one at a time become neutrally buoyant enough to sink from the ceiling. They will slowly continue to sink, but during that time (so long as they don't hit anything) they will continue to move with the air currents (which might also move them up or down)
Q: Why does the balloon move towards the mourners?
They are moving towards the AC unit, simply following the air currents in the room. We also have only two videos, presumably the most interesting ones. If the balloons moved the other way (towards the wall, or the alcove) it would be a very boring video.
Q: Why does the balloon stop at the mother and the other mourner?
A: Because the string from the balloon catches on their chair. With the mother she pulls on the string and the balloon bounces around a little. With the other mourner the string just catches for a while, then the balloon continues.
Q: Why don't we see this more often
A: Get 40 helium balloons in a room with the AC on low, wait until the balloons partially deflate and sink from the ceiling, and you will see it. In the meantime there are many videos showing similar things
Here a balloon (partially deflated, which is key) randomly moving around a room:
Another partially deflated balloon moves around the house
This one has a weight added to make it neutrally buoyant. Same effect.
Again, just following the air currents