A search party looking for five Britons kidnapped in northern Ethiopia have found three damaged vehicles.
The vehicles, discovered in the town of Hamedali, near the Eritrean border, all appeared to have been damaged either by shrapnel or an explosion.
The search in the remote Afar region, which is now in its fifth day, has found no sign of the missing Britons or their Ethiopian guides.
A Foreign Office spokesman said the discovery was "distressing".
The five Britons, all UK embassy staff and their relatives, were sightseeing with 13 Ethiopian guides when they went missing in the early hours of Thursday morning.
'Thoughts and prayers'
Eritrea has denied claims its forces took them over the disputed border, which is close to where the party disappeared.
The UK search team negotiated via satellite phone from the village of Berahle, about 37 miles (60km) from Hamedali, to gain access to the kidnap site.
The British ambassador to Ethiopia, Bob Dewar, said the group might have been the victims of "mistaken identity".
"Whatever the case, there will be those in the community who are willing and able to facilitate their safe return.
"We stand ready to hear from anyone with information relating to the group's disappearance."
He added: "My thoughts and prayers are with the families of all those involved. Their families miss them terribly and want them home."
British diplomats carried out interviews with witnesses in the area in an effort to find out what happened.
The search team is checking the vehicles for evidence
One witness claimed "around 50 men" came into the Britons' camp in Hamedali on the night of the kidnap.
The BBC's Adam Mynott said one of the discovered cars had eight shrapnel holes in the driver's door, while another had evidence of a small explosion inside the passenger seat.
A third car, belonging to the local administration, was much more badly damaged, he said.
Members of the group's luggage, shoes and mobile phones were left inside one of vehicles.
Foreign Secretary Margaret Beckett said: "We are working very closely with the Ethiopian government at all levels, as well as with others in the region, to secure their safe and early return."
The Foreign Office said the discovery of the vehicles "highlights the seriousness of the situation".
BBC security correspondent Frank Gardner said investigators were weighing up a number of possibilities, but the most plausible was that a government in the region had encouraged local tribesmen to stir up trouble along the border.
"In this case, they bit off more than they could chew, they apparently had no idea they were capturing western diplomats and the huge international operation that would then result," he said.
Head of the Afar region Ismael Ali Sero earlier said the cars used by the sightseers - a Toyota Land Cruiser and a Land Rover - were set on fire in the early-morning raid on their camp, about 800km (500 miles) north-east of Addis Ababa.
He said about 25 Eritreans in military uniform marched the group 12-18 miles (20-30 km) to Waime in Eritrea, and a local herder reportedly saw them at the Ara-ta military camp in Eritrea.
The remote Afar desert appeals to adventure travellers
The state-run Ethiopian News Agency said five of the Ethiopians who were with the kidnapped group were found near the Eritrean border late on Saturday.
One Ethiopian man told the BBC on Monday he had been one of those kidnapped, but was later released.
He said he saw the vehicles heading towards mountains on the Eritrean border, but said he did not know why the kidnappers had let him go but not the others.
Yemane Gebremeskel, of Eritrean President Isaias Afewerki's office, said Mr Ismael's claim that Eritrean troops were responsible was "crazy".
Eritrea's Information Minister Ali Abdul told the BBC's Focus on Africa programme: "I would not rule out that this is some kind of staged drama cooked up by the regime in Addis Ababa."
Tourists, who visit the area mainly to see the Danakil Depression, one of the lowest and hottest places on Earth known for its salt mines and active volcanoes, are advised to travel with an armed guard because of bandits and rebel groups.