NAIROBI, Kenya (AP) — Tens of thousands of refugees fleeing war in Sudan are struggling to find enough water to drink and cook with, leading to the deaths of an unknown number from dehydration and diarrhea, aid officials said Monday.

More than 35,000 people have fled Sudan’s Blue Nile state for South Sudan over the last month. The refugees said they fled bombing and ground fighting between Sudan’s military and a rebel group historically associated with South Sudan, the SPLM-N, the U.N. said Monday.