The Soufriere Hills volcano, which has been erupting for the past 11 years, shot a cloud of ash more than 5 miles into the sky on Monday, and authorities warned that more significant activity is possible in coming days.
The blast, accompanied by increased seismic rumbling, released gases and steam from inside a lava dome that has grown rapidly over the last week, said Dr. Vicky Hards, director of the Montserrat Volcano Observatory.
"I think it was a warning call ... of what it can do," Hards said.
The explosion near sunrise also sent a flow of volcanic material cascading down the volcano's northwest flank for 2 miles but did not immediately threaten any of the British Caribbean island's 5,000 inhabitants, Hards said. Sirens alerted people to listen to the radio for updates.
Wind blowing from the east pushed the dark gray ash over the "exclusion zone," a barren, uninhabited area extending from the 3,000-foot high volcano across the southwest to the coast. Southwest of the island is open water.
Scientists say the dome could collapse and send blistering gas and debris down the slopes of the volcano, potentially destroying homes in the low-lying Belham Valley. The volcano coughs up ash and bursts its lava cap every few months.
The Soufriere Hills volcano sprang to life in 1995, and more than half the territory's 12,000 inhabitants moved away. An eruption in 1997 buried much of the south, including the capital of Plymouth, and killed 19 people.