Mae Llywodraeth Cymru wedi ysgrifennu at tua 1,500 o berchnogion tir a thua 600 o feddianwyr eiddo ledled Cymru i'w hysbysu ei bod yn debygol bod tomen lo gyfan neu ran o domen lo segur ar eu tir.
The Welsh Government has written to more than 1,500 landowners and almost 600 occupiers of properties across Wales to inform them that they have all, or part of a disused coal tip on their land.