A mass of rock slipping down a mountainside towards a Swiss village is gathering momentum, the local authorities have warned. The village of Brienz/Brinzauls has already been evacuated with the two million cubic metre section of the mountain threatening to engulf homes. The speed of rock slippage has tripled since the 84 residents were taken to safety on May 9, it was announced on Sunday. With the mountain shrouded in mists, it has been difficult to gauge the rockslide with much accuracy over the last week. This has prevented residents from returning to their homes to pick up possessions. But the local authorities in the southwestern canton of Graubünden now say the rock movement has accelerated. In the worst-case scenario, several large rocks could tumble down the mountain reaching speeds of up to 200 km/per hour, according to Simon Löw, a geology professor at the federal technology institute ETH Zurich. This scenario has the potential to destroy the village, Löw said.