Four million people in Santiago were without tap water Sunday after unusually heavy rain pounding central Chile triggered landslides that fouled the city's water supply and forced the closure of the world's biggest copper mine, officials said.

The heavy rain flooded parts of the massive El Teniente mine, leading the state-owned copper company Codelco to halt operations there for at least three days.

The mine, located in the foothills of the Andes 150 kilometers (93 miles) south of Santiago, is being closed to let engineers and crews clean up landslides and divert streams that have "caused damage" to machinery, Codelco said late Saturday.

Temporarily closing El Teniente, which has more than 3,000 kilometers of galleries, will result in the loss of production of some 5,000 tonnes of copper, the company said.

Chile is the world's top copper producer, producing about one-third of global output.

In the capital Santiago, the national emergency response agency declared a red alert for the city of more than seven million people due to dirty water.

Heavy rains in the Andean foothills since Friday triggered landslides into the Maipo and Mapocho rivers.

Santiago Mayor Claudio Orrego said late Saturday that the cuts affect four million people, one million more than announced hours earlier.

Tap water production was down to 35 percent of normal levels, said Eugenio Rodriguez, corporate manager of the Aguas Andinas water company.

Municipal authorities activated an emergency plan that includes accessing 45 backup water sources and mobilizing more than 60 water trucks.

Thousands on Saturday flocked to stores to stock up on bottled water, and supermarket shelves were quickly left bare.

In the O'Higgins region 90 kilometers (55 miles) south of Santiago, the swollen Tinguiririca River left one person missing and about 100 homes damaged.

Rain was expected to continue throughout the weekend, leading Aguas Andinas to say that "it is not possible yet to estimate the time that service will be restored."

The Office of National Emergencies called on residents to ration water, and collect and save water if possible.