Saddle Road could become impassable due to lava over the next few days (Picture: AP)

Towns in Hawaii could be cut off if lava from the Mauna Loa volcano spreads further.

The eruption has brought a surprise tourism boom during a slow season for the city of Hilo.

Hotels in and around Mauna Loa are fully booked, while helicopter tours have seen a dramatic rise in sales.

But locals are now bracing for the worst.

There are fears the city could be divided and areas left ‘cut off’ due to overflowing lava.

Molten rock could make Saddle Road impassable and force drivers to find other routes between the north and south of the island.

‘I am very nervous about it being cut off,’ said Frank Manley, a licensed practical nurse.

If the road closes, he will have to drive two-and-a-half to three hours in each direction.

The number of visitors to the island has increased since the volcano eruption (Picture: AP)

Drivers are worried about how they will access key services if the road becomes blocked (Picture: AP)

The lava is moving at a rate which means it could hit the road early next week, but its path could change course.

On Friday, US Geological Survey scientists said the slow-moving flow was coursing around 2.7 miles from the road.

The state Department of Transportation has already taken steps to remove potential traffic obstacles on the northern coastal route by reopening a lane across Nanue Bridge that was closed for repairs.

If Mauna Loa follows historical patterns, the eruption is expected to continue for one to two weeks.

Cars wait in traffic along Saddle Road, with occupants waiting to view the Mauna Loa volcano (Picture AP)

Lava started erupting at the end of November (Picture: AP)

Hawaii Democrats Ed Case and Kaiali’i Kahele sent a letter to President Joe Biden warning Hawaii County would require ‘immediate help’ to keep island communities safe if lava flow blocks the highway.

Restricted access could impact one of the island’s largest hospital’s which is located on the east side.

Hawaii County Councilor Susan ‘Sue’ L. K. Lee Loy, who represents Hilo and parts of Puna, said she is concerned about big lorries travelling across aging coastal bridges.

‘It’s going to take a lot to rethink how we move about on Hawaii Island,’ she said.

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The lava is moving at a rate which means it could hit the road early next week.