La Palma's volcano suddenly stopped erupting this morning - before restarting several hours later with 'explosions' heard miles away.
The brief hiatus, during which volcanic activity dropped off almost completely, sent scientists scrambling to work out what it means - amid warnings that the eruption is not over and could simply be entering another new phase.
Volcanologists theorised that a vent could have become briefly blocked or that underground channels may be shifting, possibly diverting lava elsewhere and opening up a new vent.
Meanwhile, new lockdown orders were issued for three areas today as lava that has already been expelled from the volcano continued to trickle towards the ocean.
Angel Victor Torres, president of the Canary Islands, said molten rock may reach the ocean 'within hours' where it will release a cloud of poison gas as it mixes with sea water - warning nearby residents to stay in their homes with their windows locked.
Those who are directly in the path of the lava flow have already been evacuated.
EU weather satellites captured the first clear image of La Palma's volcano without clouds on Sunday, showing the extent of the devastation it has caused
The volcano continued to erupt overnight Sunday but stopped around 10am Monday, with scientists scrambling to figure out why
A couple hold hands as they watch lava erupt from the La Palma volcano overnight Sunday, just hours before the eruption stopped
Scientists warn it is unlikely the volcano has stopped erupting for good, and may simply be gearing up for a 'big burst' later in the day
The new lockdown order covers the areas of San Borondon, Marina Alta, Marina Baja and La Condesa.
La Palma's new volcano, which is located on the Cumbre Vieja ridge on the south of the island, began erupting on September 19 and has been spewing out a continuous stream of lava and ash ever since.
Experts previously said the eruption could last between two weeks and three months, making Monday's shut-down unusual.
There have been periods of high and low activity since the eruption began, by Monday marked the first time it has stopped completely.
Geologist Nahum Mendez Chazarra told Spanish newspaper LaSexta that the volcano could simply be 'recharging' before a burst of activity.
David Calvo, of the Canary Islands Volcanological Institute, told La Vanguardia that another explanation could be that a vent has become blocked.
That could mean the maga is diverting to another part of the island, Mr Calvo added, pointing out that a cluster of earthquakes has been detected around 10 miles south of the eruption site today, close to the Teneguía volcano that erupted in 1971.
'It may be that there is a magma migration in the interior of the island... towards more accessible areas, or that there is a readjustment of the structure of the island in response to the exit of the magma.
'There is more magma,' he added. 'That it will come out is not certain.'
Monday's slow-down in activity comes after a very active weekend, which saw a new vent open in the volcano on Saturday - raining ash down on the eastern side of the island which until-now was largely untouched by the eruption.
La Palma's airport was closed entirely on Saturday and for most of Sunday due to the ash-fall, amid fears it could damage the engines of aircraft.
A map showing where the lava flow has reached (in orange), where the ash plume has covered (in grey), and the areas placed under lockdown today (top left)
Ash has been pouring out of the volcano since late last week, blanketing nearby towns as officials warned it can cause lung damage if inhaled
People carry umbrellas through Santa Cruz de La Palma, the island's capital, on Sunday to protect themselves from ash falling from the volcano
A street-clearing vehicle is used to sweep ash off the roads of La Palma after it rained down from the erupting volcano
The airstrip reopened Sunday evening after the runway was cleared, though all incoming and outgoing flights were cancelled by transport firms.
It appeared that flights were taking off and landing on Monday morning, with only one inbound and one outbound flight - both to and from Madrid - cancelled.
Some 6,000 people have been evacuated from their homes due to the eruption, which was proceeded by a cluster of earthquakes - putting authorities on alert and allowing them to avoid any casualties.
While ash and lava has blanketed an area on the west side of the island, life on the rest of La Palma - which is roughly 22 miles long and 12 miles wide at its broadest point - has been largely unaffected.
'We're not in a state of total alarm,' the technical director of the volcano emergency response unit, Miguel Angel Morcuende, told a news conference.
'Life on the island is continuing, though those close to the eruption are facing difficulties.'
The volcano initially blenched out lava and toxic fumes, but began raining down ash late last week after entering 'an explosive new phase', experts said.
Officials said the falling volcanic ash isn't a threat to public health, but cleaning it up can be hazardous for people's lungs and eyes.
They urged people to wear a face mask, gloves and eye protection, as well as trousers and long-sleeve shirts, when removing ash.
Some 25,000 metric tons of sulfur dioxide are being emitted from the crater every day but don't pose a health threat, officials said.
As the airport closed, long lines formed at ports as people tried to catch ferries off the island to its neighbours - where flights were still running.
Two rivers of lava are slithering down hillsides: One to the north, where molten rock from a new fissure is spreading over an area where lava spread and hardened last week, and another one south of it which is advancing at about 100 feet per hour.
The temperature of the lava is around 1,250 degrees Celsius (2,282 degrees Fahrenheit).
Pope Francis said on Sunday that he was praying for all those affected by the volcano, dedicating a prayer to them at the end of his weekly noon blessing in St. Peter's Square.
'I think especially of those who have been forced to leave their homes,' he said.
Ash from the volcano caused the island's airport to close at the weekend, diverting people towards ferries to neighbouring islands - where planes were taking off
A large queue forms for a ferry off La Palma on Sunday after an ash plume from the erupting volcano shut the airport