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Hawaii and parts of California were on tsunami alert early Thursday after a huge 8.3-magnitude earthquake struck off the coast of north Chile.

It prompted the U.S. Coastguard to urge the public in Hawaii to use “extreme caution” in waters around the main islands. People should prepare for "strong currents and surf throughout the main Hawaii Islands," they said.

The tsunami was due to start in Hawaii at 3.11 a.m. local time (9.11 a.m. ET) and in California at 4.46 a.m. local time (7.46 a.m. ET), the National Tsunami Warning Center said.

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The Pacific Tsunami Warning Center had originally issued a watch for Hawaii, saying a tsunami may have been generated by Wednesday's earthquake. The watch was later downgraded to an advisory saying that data indicated there would be no major tsunami in the state but sea-level changes and dangerous currents could pose a threat to those in or near the water.

The Hawaii Emergency Management Agency said state officials were standing by late Wednesday and awaiting updates from the warning center.

Update: Hawaii under a Tsunami Advisory. No major tsunami expected for the state. However, sea level changes and strong currents may occur. — NWSHonolulu (@NWSHonolulu) September 17, 2015

On the Big Island, officials were bracing to be the first island affected, county spokesman Ilihia Gionson said. "It's too early to tell," he said. "This early it's best to just stay informed."

The advisory was issued after a powerful earthquake shook Chile, forcing more than one million people to evacuate their homes.

Chile's President Michelle Bachelet said at least five people died. Damage as reported in some coastal towns that saw flooding from small tsunami waves.

The National Tsunami Warning Center said California “should not expect widespread inundation” but added that waves could be dangerous “many hours after initial arrival time.”

“The tsunami advisory remains in effect for the coastal areas of California from San Onofre state beach California, which is located 45 miles southeast of L.A., to Ragged Point, California, which is located 50 miles northwest of San Luis Obispo.”

“If you are located in this coastal area, move off the beach and out of harbors and marinas.”