Residents on the western coast of La Palma have been told by authorities to lock down and seal doors and windows with tape and wet towels to ward off toxic gases spewed by lava from the Cumbre Vieja volcano.
People should “protect breathing tracts with a wet cloth covering the mouth and nose”, emergency services said.
This came as the islands’ government set up a 3.5km (2 mile) exclusion zone on land and a two nautical mile perimeter at sea to keep people safe.
Ten days after the volcanic eruption, lava gushed down a cliff into the Atlantic sea early on Wednesday in the Playa Nueva area, sending a pyramid of red hot lava 50 metres high above the sea.
“A ‘delta’ of lava has formed which is gaining ground in the sea,” tweeted the Spanish Oceanographic Institute.
Experts had warned that the entry of the white-hot magma into the sea was likely to release clouds of acidic gas into the air, which could irritate the skin, eyes and respiratory tracts, possibly causing breathing difficulties.
Sea life could also be affected by the lava mixing with sea water, officials said.
However, windy conditions overnight blew the gas towards the sea, reducing the risk, said Ruben Fernandez, head of the Canary Islands’ Pevolca volcanic emergency committee.
“It is still relatively dangerous,” warned Mr Fernandez in an interview on Spanish radio RNE.
About 300 residents of the town of Tazacorte, a village near the sea, were evacuated on Tuesday.
All roads to the southern part of the island have been closed off, except to emergency vehicles.
Canary Islands regional president Angel Victor Torres said it was a “dangerous moment” as “1,000C lava entered 22C water” because of the emissions, toxicity and explosions.
“What we hope now is that (the lava) stops expanding and does not affect more homes,” he added.
Since the eruption of Cumbre Vieja, thousands of people have been evacuated and more than 600 houses have been destroyed.
Banana plantations, which account for about 50 per cent of the economy in La Palma, have also been destroyed.
La Palma airport remains open but flights have been delayed.
Spain classified La Palma, an island at the north of the archipelago off the west coast of Africa, as a disaster zone on Tuesday and assigned €10.5m in financial support for the island.
Isabel Rodriguez, the Spanish government spokesperson, said 107 houses will be immediately acquired for the families that have been made homeless by the volcanic eruption.
Charities and companies across Spain are raising money for families whose homes have been destroyed.
