Officials issued alerts on the island chain of St Vincent and the Grenadines, home to more than 100,000 people, as scientists rushed to study the renewed activity.
The government raised the alert level to orange for the volcano La Soufriere indicating it could erupt within 24 hours.
La Soufriere began spewing ash along with gas and steam, in addition to the formation of a new volcanic dome caused by lava reaching the Earth’s surface, the Caribbean Disaster Emergency Management Agency said.
An eruption by La Soufriere in 1902 killed more than 1,000 people.
Authorities on the Caribbean island of Martinique, an overseas French territory, are also watching the Mount Pelee volcano after tremors became more frequent last month.
In December, authorities issued a yellow alert due to seismic activity under the mountain, the first alert of its kind issued since the volcano last erupted in 1932, Fabrice Fontaine, from Martinique's Volcanological and Seismological Observatory, told the Associated Press.
Scientists have said the simultaneous increase in activity of La Soufriere and Mount Pelee is not linked.
“It's not like one volcano starts erupting that others will,” volcanologist Erik Klemetti, at Denison University in Ohio, said. "It falls into the category of coincidence."
He said the activity is evidence that magma is lurking underground and percolating towards the surface, although he added that scientists still do not have a very good understanding of what controls how quickly that happens."
"The answers are not entirely satisfying," he said. "It's science that's still being researched."
Seventeen of the eastern Caribbean's 19 live volcanoes are located on 11 islands, with the remaining two underwater near the island of Grenada, including one called Kick 'Em Jenny that has been active in recent years.
Additional reporting by agencies
This story was amended on 4/1/21. Some early reports said the government had urged people living near the volcano to evacuate their homes, but this turned out not to be the case. The article was edited to reflect this.
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