The United Nations Office for the Coordination of Humanitarian Affairs (OCHA) said on Tuesday it is concerned about the deteriorating humanitarian situation in eastern Chad amid a massive influx of refugees and returnees from neighboring Sudan. More than 55,000 Sudanese refugees and 39,000 Chadian returnees have been registered in Chad's Ennedi-Est and Wadi Fira provinces since violence escalated in Sudan's North Darfur state in April.