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Aton Chile, Associated Press
Residents watch the rising flood waters of the Copiapo River, in Copiapo, Chile, Wednesday, March 25, 2015. Unusually heavy thunder storms and torrential rains that began on Tuesday have blocked roads, caused power outages and affected some 600 people on this normally dry region.

SANTIAGO, Chile — Communities in a desert region of northern Chile struggled Thursday to cope with rain-provoked flooding that has claimed the lives of at least four people, knocked out power and cut off roadways.

Thunderstorms with torrential rains moved into the Atacama desert region Tuesday, causing the Copiapo River to overflow its banks.

Fears of mudslides prompted authorities to evacuate thousands from their homes.

The flooding is "the worst rain disaster to fall on the north in 80 years," Deputy Interior Minister Mahmud Aleuy said Thursday.

TV images showed brown, muddy waters flooding the streets and reaching a hospital in Copiapo city. Some people living along the river had to be rescued by helicopter because roads were blocked by water and mud. TV footage showed several families waiting on the roofs of their homes, including a man who had punched a hole through his roof to save his toddler.

At least four people have been killed and 22 people were listed as missing in three communities hit by flooding, Aleuy said.

Desperate family members of the victims took to Twitter pleading for help finding their loved ones.

The government declared a state of emergency, putting the region under military control, and President Michelle Bachelet flew to the area Wednesday evening to observe the problems first hand.

"We're living an extremely difficult situation," she said. "The previous forecast was that there was a huge drought here, so the rains were not necessarily seen as a catastrophe. Foreseeing was really difficult because no one knew."

The heavy rains caused by a cold front came after several days of high temperatures and a drought that stoked raging wildfires in Chile's south central regions. The fires have burned nearly 93,000 hectares in the 2014-2015 season, far above the annual average of 59,300 over the previous five years.

Earthquake-prone Chile is no stranger to the forces of nature. The national geological service Sernageomin said residents should be on alert due to increased activity at the Villarica Volcano in the country's south, which erupted on March 3, forcing evacuations and disrupting air traffic.

Chile's state-run copper giant Codelco said the flooding prompted it to suspend mining operations due to blocked roads. Mining sites themselves, including the world's largest open-pit copper mine, were not directly affected, it said.

Luis Andres Henao on Twitter: https://twitter.com/LuisAndresHenao