Lava entered the ocean from a third flow, marking the third week of a Hawaii volcano eruption that has opened up nearly two dozen vents in rural communities, destroyed dozens of buildings and shot miles-high plumes of ash into the sky.

Low lava fountains were erupting from a nearly continuous 2-mile-long (3.22-kilometer) portion of the series of fissures that have opened up in the ground, scientists said Thursday. The fountains were feeding channelized lava flows down to the coast. The eastern-most channel split, creating three ocean entries Wednesday.

Since the eruption began on May 3, Hawaii County has ordered about 2,000 people to evacuate from Leilani Estates and surrounding neighborhoods.

Hawaii officials have said they may need to evacuate a thousand more people if lava crosses key highways and isolates communities in the mostly rural part of the island where the Kilauea volcano is erupting.

A blocked highway would cut people off from the only route to grocery stores, schools and hospitals.

The U.S. Marine Corps said Thursday that it has sent two CH-53E Super Stallion helicopters from a base near Honolulu to help if more evacuations become necessary. Each helicopter can carry 50 passengers.

The volcano has opened more than 20 vents in the ground that have released lava, sulfur dioxide and steam. The lava has been pouring down the flank of the volcano and into the ocean miles away.

Lava has destroyed 50 buildings, including about two dozen homes. One person was seriously injured after being hit by a flying piece of lava.

There continues to be intermittent explosions at the summit that have been sending plumes of ash into the sky. On Wednesday, the volcano belched a plume that reached about 7,000 feet (2,133 meters), scientists said. Right before the explosion, there was a 3.9 magnitude earthquake at the summit.

"We are kind of in this steady state," said Wendy Stovall, a scientist at the U.S. Geographical Survey. There's no indication about whether lava volume will increase or decrease, she said. The continued explosions are expected to "last a little while longer."

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This story has been corrected to reflect the third lava flow began entering the ocean on Wednesday, not Thursday, based on new information from officials.

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AP journalist Audrey McAvoy contributed to this story.

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