Lava oozing out of Mauna Loa inching closer to main highway on Hawaii's Big Island

The lava flowing out of Mauna Loa, the world's largest active volcano located on Hawaii's Big Island, is inching closer to a main highway, according to officials.

The lava is flowing out of Fissure 3 in the northeast rift zone and is now just 3.6 miles from Saddle Road, a main highway that runs east to west through the center of the island and a route often used to travel between Kona and Hilo, the U.S. Geological Survey tweeted just before 10 a.m. local time.

Volcanic gas plumes are lofting high and vertically into the atmosphere, according to the Hawaii County Civil Defense.

Fissure 3 remains the dominant source of the lava and is feeding flows that are moving downslope toward the highway, according to the USGS. Around 7 a.m. local time, the lava fountains were reaching up to 82 feet, the USGS confirmed. Lava fountains have also formed at Fissure 4, which is emitting smaller fountains of hot magma and is also flowing downslope toward the road.

Both fissures are feeding flows that are advancing northeast at .08 miles per hour toward the highway.

The flows are approaching a relatively flat area and will begin to slow down, spread out and inflate, according to the Hawaii County Civil Defense. It could take another two days for the lava to reach the highway, officials said.

However, seismic detection of tremors in the location of the currently active fissures, indicates that magma is still being supplied and activity is likely to continue, according to the Hawaii County Civil Defense.

Emergency managers are beginning to ramp up planning, as the lava threatens the main route to travel east and west on the island, Talmadge Magno, an administrator for the Hawaii County Civil Defense, said on Wednesday. Magno is especially concerned about the "thousands of residents and visitors" who have flocked to the highway to view the eruptions, which are exacerbating the safety hazards, he said.

In addition, Pele's hair, or strands of volcanic glass, are falling in the Saddle Road area, officials said.

Dramatic video released by the USGS shows the volcano dispelling a nearly six-story wall of exploding lava.

Ash and lava began spewing out of the volcano on Sunday around 11:30 p.m. and has continued into Wednesday.

This is the first time Mauna Loa has erupted in nearly 40 years. The last time it erupted was in March and April 1984. The volcano is so large it takes up more than half of the Big Island

Geologists do not expect any activity outside of the northeast rift zone, and there are still no threats to populated areas, as there are no homes downslope from the northeast rift zone, according to the USGS.

Since the eruption is occurring to the northeast, where the peak's slope seaward is more gentle, it would take weeks of a continuous eruption for it to reach Hilo, Michael Poland, research geophysicist for the USGS Cascades Volcano Observatory, told ABC News earlier this week.

However, officials have advised residents at possible risk from Mauna Loa lava flows to review preparedness and refer to Hawaii County Civil Defense information for further guidance.

ABC News' Jennifer Watts contributed to this report.