Immediate inspections of the old coal tips on the mountains in the Rhondda are underway as people living close to them told ITV News they are concerned a more serious incident could happen.
One landslide which was captured on camera in Tylorstown shows coal dramatically tumbling down the mountain.
Several others are believed to have occurred at the weekend including on the mountain road from Blaenllechau to Llanwonno.
Gerald Durham witnessed the landslide happening in Tylorstown on Sunday and told ITV News it reminded him "immediately" of the Aberfan disaster.
Gerald's father Cliff is a former coal miner and said the scenes also reminded him of Aberfan.
"I worked in a local colliery in Maerdy and as soon as I saw this, I thought of Aberfan straight away."Believe me - you don't want to see that again.
"There's tonnes and tonnes of coal still around. The authorities should drill it so the water could go down but they can't leave it like that.
"They've got to take it away because it could come again."
Bill Powell, 83, said all of the waste tips in the area need to be inspected.
"I think all these tips should be checked to see if there's any water beneath them.
"How safe are they? That's what I'm thinking. If that one in Wattstown comes down, it would be one hell of a catastrophe.
Watch the full report by Rob Osborne:
The Coal Authority told ITV News they are not responsible for any of the sites that collapsed at the weekend.
Leader of Rhondda Cynon Taf Council Cllr Andrew Morgan said discussions were underway with Natural Resources Wales to determine who owns the land.
"Engineers are on site right now. We will be carrying out inspections not just now but also going forward what is needed - establishing exactly who is responsible for this area is going to be key but if there is longer work needed, to ensure safety of the public and those properties, then I would expect it to be funded and we are in discussions with the Welsh Government about that."
"Later today I will be making the public aware we are setting up a recovery board - that will be in place tomorrow", he added.
"We will be making £1million of emergency funding available. Cost is not an issue at present - safety is paramount."