Police in Ethiopia uncovered a grave containing at least 200 bodies along the border between the strife-torn Oromiya and Somali regions, state-affiliated media said.
The mass grave was found during an investigation of a former administrator of the Somali region facing trial on charges of human rights abuses and stoking clashes, the Fana Broadcasting Corporation said, quoting police officials.
It did not give further details.
Abdi Mohammed Omer was forced to resign on August 6 and was arrested weeks later after violence broke out in the provincial capital, Jijiga.
Rights groups routinely accuse his administration of abuses including torture, while some witnesses claim he ordered paramilitary raids on civilians in Oromiya province after ethnic clashes last September.
The region has been plagued by violence as government fought the secessionist Ogaden National Liberation Front before a peace deal last month.