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By John McPhaul

CINCHONA, Costa Rica, Jan 11 (Reuters) - Rescue workers with dogs were threatened by mudslides on Sunday as they searched among collapsed houses for survivors of an earthquake that killed more than 20 people in a Costa Rican town last week.

Sniffer dogs stumbled through rubble around the village of Cinchona, on the flank of the Poas Volcano, where rescuers believe more victims may be found in a restaurant crushed by a landslide after Thursday's 6.1-magnitude quake.

"We think there are two people in this house, so we're going to cut through the roof and dig to see what we can find," said rescuer Andres Madrigal, who later recovered the bodies of two small children and a woman from the house.

A Red Cross official had earlier put the death toll at 20. Authorities visited shelters crammed with hundreds of Costa Ricans in the hopes of narrowing a list of missing people.

Daily rain has added to the danger of more landslides, said National Emergency Commission official Victor Falla. "Some (ground shifts) are so strong that work has to be suspended," he said. "Everyone, including the rescuers, has to run."

Houses in the jungle region teetered on the edges of cliffs created by the earthquake. In one area at risk of collapse, abandoned dogs guarded homes left by residents evacuated to shelters.

Colombia and the United States have sent military helicopters, rations, bottled water and electric generators to help the Costa Rican government, which does not have an army.

Hundreds of people stranded by blocked roads have been moved to shelters or evacuated by air to the capital San Jose.

Five British tourists who were unaccounted for have since been located and are safe, embassy official Ericka Phillips told Reuters.

"We have had no reports, of British or any other foreign nationality, of deaths, injuries or missing people," she said.

Costa Rica is a popular tourist destination because of its lush natural parks, volcanoes and rich wildlife, but it is prone to natural disasters like the rest of Central America. (Additional reporting by Manuel Carrillo in San Jose, Noel Randewich and Tomas Sarmiento in Mexico City)

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