A Canary Islands volcano that has been erupting for over a week fell silent Monday as coastal residents were confined over toxic gas fears when the lava hits the sea.

La Cumbre Vieja, which straddles a southern ridge in La Palma in the Atlantic archipelago, erupted on September 19, spewing out rivers of lava which have slowly crept towards the sea.

But on Monday morning, there was no lava and ash emerging, with the week-long rumble of the eruption fading to silence, an AFP correspondent at the scene said. 

It was not immediately clear whether the eruption had stopped completely or merely paused, as smoke was still emerging from the top. 

"Volcanic activity in La Palma has reduced significantly in the last few hours. We must be very vigilant about how it evolves because the scenario can change quickly," Madrid's Institute of Geosciences tweeted. 

"It seems the volcano has entered a phase of decreased activity. We will see how it evolves in the coming hours."

And the Involcan volcanology institute gave a similar assessment.

"In the last hours, the volcanic tremor has almost disappeared, as well as the... explosive activity," it tweeted.

Contacted by AFP, Involcan was unable to say whether the eruption had finished or just paused, with a spokesman saying its experts were "evaluating the different scenarios". 

Overnight, the inhabitants of several coastal areas were ordered to stay at home to avoid harm from the release of toxic gases when the lava finally reaches the sea, a process which has been much slower than initially expected. 

When the molten lava enters the ocean, experts warn it will send clouds of toxic gas into the air, as well as explosions and a fragmentation of the lava, which shoots outwards like bullets. 

The authorities have set up a no-go zone to head off curious onlookers.