The fiery flow from the Soufriere Hills volcano torched the colony's customs offices, a supermarket, a clothing store, a church and a dozen houses, but no one was hurt, according to the government spokesman, Richard Aspin. "We were expecting it," Mr Aspin said. "But there's the distress of seeing buildings burning in the capital for the first time."
The heightened activity in the rumbling mountain was the worst since 25 June, when pyroclastic flows of rock, gas and ash swept through several villages, killing 19 people. Those were the first deaths attributed to the volcano since it roared to life in July 1995 after nearly four centuries of dormancy.
Plymouth, a once-bustling town of 5,000 and the heart of social life in the colony, has been abandoned for much of the past two years.
Residents in the island's south end, where the capital is located, were last evacuated to the northern "safe zone" in April 1996. Since the volcanic activity began, the island's population has dropped from 11,000 to 5,200 as residents leave for Britain or neighbouring islands to find work and safer homes.
Three major pyroclastic flows swept down the mountain late on Sunday and early yesterday, sending tons of debris tumbling into Fort Ghaut, a river valley that runs through the heart of Plymouth, Mr Aspin said.
The hot rock and ash set a score of buildings on fire before reaching the sea. The fires were the first caused by the volcano in Plymouth. "We're letting them burn themselves out. It's too dangerous to go in," Mr Aspin said. A resident who ventured into the danger zone and was trapped by the flows was rescued by sea yesterday, unharmed, he said. The mountain belched clouds of ash, leaving thick dust in the air. Residents were cautioned to wear dust masks when they ventured outside.
Since the deaths on 25 June, the situation is policing itself, Mr Aspin said. "People just don't go in any more," he added.
Richard Robertson, chief scientist at the Montserrat Volcano Observatory, said the latest pyroclastic flows were part of a pattern that volcano observers had seen before. "We are entering a period of elevated activity," he said, adding that the northern half of the island was still considered safe.
"The north at the very most will be affected by ashfalls," he said. "We don't see any major problems there, even with this new activity."
The volcano's dome, a giant pile of debris pushed up from the centre of the mountain, contained 2.72 billion cubic feet of material at last estimate, Mr Robertson said.