Several Britons linked to UK Government departments are among those missing - feared kidnapped - in eastern Ethiopia.
A group of at least 15 western tourists on a trip to look at geological sites have gone missing 500 miles north of the capital Addis Ababa.
They include people with links to the Foreign Office, British Council and the Department for International Development (DfID), the Foreign Office said.
Rossanna Moore, wife of Michael Moore, the director of the British Council in Ethiopia, is thought to be among those missing.
The Foreign Office refused to confirm the number of people missing, although earlier reports said five Britons were unaccounted for.
A further 10 French nationals are believed to be among those who disappeared during a trip to the remote region.
A Foreign Office spokeswoman said: "We can confirm that a group of Western tourists is missing in eastern Ethiopia, including a number of British nationals with links to the British Council, the Foreign and Commonwealth Office and DfID.
"The group was on an organised tour in a well-known tourist region with geological features.
"We cannot at this stage confirm anything else. Our embassy is working closely with the government of Ethiopia and urgently trying to get a clear picture of what is happening."