Ethiopian authorities have detained more than 70 drivers working with the UN, an internal email at the organisation has shown.
It comes amid reports of widespread arrests of ethnic Tigrayans in areas under government control.
The ethnicity of the drivers was not clear.
These are in addition to the detained drivers, said the email, which was seen by Reuters.
“We confirm that 72 outsourced drivers contracted by WFP [World Food Programme] have been detained in Semera,” a UN representative told Reuters, referring to the capital city of the north-eastern region of Afar.
“We are liaising with the government of Ethiopia to understand the reasons behind their detention.”
Government official Legesse Tulu and Ministry of Foreign Affairs official Dina Mufti did not immediately respond to a request for comment on the detention of the drivers.
On Tuesday, when asked about the detention of UN contractors such as drivers, a UN representative in New York said the organisation was investigating.
The head of the state-appointed Ethiopian Human Rights Commission said on Tuesday they had received hundreds of reports of Tigrayans being detained in the capital.
Police have denied making ethnically motivated arrests, saying they are only focused on supporters of the Tigrayan forces fighting against government forces.
War broke out last year between the federal government and the Tigray People's Liberation Front, which used to dominate the ruling coalition in the country.
On Wednesday, the UK government advised against all travel to Ethiopia and urged British citizens to leave the country “while commercial routes are available".