With rescue operations continuing in the flood-ravaged south, where at least 364 people have died in the past week and up to 8,000 are still stranded, US naval engineers began relief work in the inundated east.
Troops from the US military base in nearby Djibouti arrived in the town of Dire Dawa, about 500 kilometers east of Addis Ababa where 256 people were killed and more than 6,000 left homeless.
A team of 35 navy "Seabees" brought with them 52 large tents to house the displaced and equipment to construct sanitation facilities amid growing fears of the spread of water-borne disease among the survivors.
A series of flash floods in the east, north and south of the impoverished country followed by unusually heavy seasonal rains that caused rivers to burst their banks.
Heavy downpours continue in the Ethiopian highlands, causing further rises in water levels.
At least 15,000 people were left homeless in an area between Dire Dawa and the capital when the Awash River overflowed.
The confirmed national death toll is hovering at 626, but aid workers and local authorities expect it to rise sharply as hundreds are unaccounted for and many areas can't be reached.
Some 73,000 people have been affected by the floods, according to the United Nations.
Up to 8,000 are stranded in 14 submerged villages in the Omo River valley, where army airborne search and rescue teams have been plucking survivors from roof and tree tops and dropping food and clean water.