ZURICH (Reuters) - Emergency services with helicopters, drones and rescue dogs searched on Saturday for three people who were missing after violent downpours caused floods and landslides in southwestern Switzerland.

MeteoSchweiz, the government's office for weather and climate, said 124 mm (4.88 inches) of rain fell in Mesolcina valley in the canton of Grisons on Friday, with 63 mm (2.48 inches) falling in a one-hour period.

"It was not the level of rain, but the concentration of rain in such a short period of time which caused the problems," a spokesman for MeteoSchweiz said.

"This concentration of rain happens only once every 30 years."

Several rivers burst their banks in Mesolcina valley, also known as Misox, covering roads, fields and villages with rubble, earth and wood.

Three houses and three cars were swept away by water in the village of Sorte, Grisons police said. Two police officers were able to escape from their vehicle which was submerged up to its roof.

Four people were initially reported missing, although a woman was later found under rubble and taken to hospital in nearby Lugano. A search was still underway for three other people who police said could have been in their homes when the flooding took place.

Police urged people not to travel to the region as many roads were closed. Five villages were without electricity.

In the western canton of Valais, 230 people were evacuated since Friday after heavy rainfall caused flooding and mudslides.

The road and railway line to the town of Zermatt, next to the Matterhorn mountain, was also closed, although police said they hoped to reopen the routes on Saturday evening.

(Reporting by John Revill; Editing by Frances Kerry)