The volcano, which first erupted on the island of La Palma more than a week ago, stopped releasing large clouds of smoke and lava for a few hours on Monday. However, local scientists said it has now restarted.
On Twitter, the Canary Islands volcano institute posted pictures of the "ash emissions that are being observed in the last hours".
The Madrid-based Institute of Geosciences, which previously said the volcano had reached a "low activity phase", tweeted footage of "little explosions".
The volcano on La Palma, part of Spain's volcanic Canary Islands, erupted on September 19. The prompt evacuations of more than 6,000 people helped avoid casualties, while over 5,000 buildings have been buried.
On Sunday, a church on the Spanish island of La Palma crumbled after lava entered the town of Todoque. The dramatic scene, caught on camera by TV Canarias, showed a cloud of dense smoke engulfing the bell tower of the church before it collapsed.
A church disappears from the horizon after being toppled by lava
On the same day, a huge cloud of ash prevented flights in and out of La Palma.
La Palma airport Spanish airport authority reopened on Sunday after teams cleaned ash from the runway.
Canary Islands airline Binter said: "We resume the flights with La Palma starting at 1pm today. If the situation remains the same, we will continue with the flights planned in our regular schedule".
ENAIRE, the islands' air navigation manager, tweeted that it operated 759 flights on Sunday.
Meanwhile, long lines formed at the island’s port to catch ferries off the island.
Some evacuees in La Palma have been allowed to return to their homes amid low seismic activity, while authorities took stock of the damage caused.
On September 21, ITV News Correspondent Dan Rivers reported on swimming pools bubbling up as lava spread through the streets
“We’re not in a state of total alarm,” the technical director of the volcano emergency response unit, Miguel Ángel Morcuende, told a news conference on Sunday.
“Life on the island is continuing, though those close to the eruption are facing difficulties.” 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,” the pontiff said. This month’s eruption is the first on La Palma since 1971.