The ash blanketed this British territory in a layer so thick tree branches snapped under the weight, said Richard Herd, director of the Montserrat Volcano Observatory. The damage to vegetation was significant, he said.
"There's no one in the area right now but as a precaution we're asking people in surrounding areas to stay indoors. There's still a chance of more explosions and rock fall," he said.
On St. Croix, a man died when his car swerved off the road because of poor visibility due to the ash, U.S. Virgin Islands police said.
Houses and cars across much of the Dutch Caribbean territory of St. Maarten wore a grimy coat of ash. Residents were told to stay indoors or wear surgical masks.
American Airlines canceled some 50 flights from Puerto Rico to islands in the area, including St. Thomas, St. Maarten, Anguilla, Guadeloupe, Dominica and St. Kitts.
"There is a lot of ash and to avoid any problems we decided to cancel the flights," said Minnette Velez, an American spokeswoman in San Juan, the capital of the U.S. territory.
Continental, Winair, LIAT, Caribbean Sun and Caribbean Star also suspended operations in affected areas.
Part of the volcano's dome collapsed late Saturday, sending a torrent of mud and ash down into the adjacent Tar River Valley and pelting distant houses and buildings with rocks.
In October, 300 people living near the valley were evacuated after scientists warned the volcano's dome had shifted its growth toward the north.
The Soufriere Hills volcano sprang to life in 1995, chasing away more than half the British Caribbean island's population. A 1997 eruption buried much of the south, including the capital, Plymouth, and killed 19 people.
Today, the peak still casts a reddish-orange glow at night. Scientists monitor it and report any changes to the island's 4,500 residents, who live in northern areas declared safe.
Once a bustling island where sheep and cattle roamed the hills and chartered yachts pulled in weekly on tourist runs, Montserrat's economy has been hit hard by losses in tourism and farmland in the south, which is now uninhabitable under mountains of volcanic, gray ash.
By Bennette Roach