Clouds of thick ash from the volcano on La Palma on Thursday forced the island's airport to close for the second time since the eruption began last month, Spain's airport authority said. 

"La Palma airport is not operational due to the accumulation of ash," AENA tweeted, with a spokeswoman telling AFP "some cleaning work needs to be done" on the runways before it would reopen. 

The airport was briefly shut on September 25 after a thick cloud of black ash forced airlines to cancel flights. 

Although it was reopened a day later, flights did not resume until September 29. 

It has been 18 days since La Cumbre Vieja began erupting, forcing more than 6,000 people out of their homes as the lava burnt its way across huge swathes of land on La Palma, one of Spain's Atlantic Canary Islands that lie off the northwestern coast of Morocco.

The AENA spokeswoman said Thursday's airport closure "may not last very long". 

David Calvo, spokesman for Involcan, the Canary Islands volcanic institute, said the volcano was producing "a lot of ash", saying a change in the wind meant the ash cloud was "affecting the airport".

On Wednesday evening, local airline Binter had said it was cancelling all flights in and out of La Palma.

"This suspension will last until conditions improve and we can fly safely," Binter tweeted, with rival airline Canaryfly also suspending flights. 

An AFP correspondent at the scene said the glowing lava streams could still be seen for miles around on Wednesday night. 

By Thursday morning, images released by the Spanish Geological and Mining Institute (IGME) showed a thick cloud of black smoke billowing from the crater of Cumbre Vieja. 

The 100-acre lava delta

Pumping out endless streams of molten rock with a temperature of over 1,000 degrees Celsius (1,832 degrees Fahrenheit), the volcano spewed out streams of lava that consumed more than 1,000 acres (422 hectares) of land as it cut a six-kilometre (3.5-mile) path to the sea. 

Once it reached the coast on September 29, it cascaded into the sea, creating a growing lava delta that is currently the size of 60 football pitches (100 acres), Involcan data shows. 

And figures released on Tuesday by the islands' regional government said more than 605 of the destroyed buildings were homes. 

It has also destroyed huge swathes of banana plantations -- the chief cash crop on La Palma. 

"The damage is enormous.. We are talking about a third of the banana production of the entire Canary Islands," the archipelago's regional head Angel Víctor Torres said last week, indicating the current harvest had been "completely lost".

The eruption on La Palma, an island of some 85,000 people, is the first in 50 years. 

The last was in 1971 when another part of the same volcanic range -- a vent known as Teneguia -- erupted on the southern side of the island. 

Two decades earlier, the Nambroque vent erupted in 1949.