A dome over the crater of Montserrat's volcano has partially collapsed, spewing ash an estimated 40,000 feet into the Caribbean sky, scientists said Tuesday.

No one was injured, but residents were temporarily evacuated late Monday as a precaution, said Roderick Stewart, director of the Montserrat Volcano Observatory.

About 120 people who live north of the volcano drove away in their cars to stay at government buildings and returned later, said James White Jr., acting director of the Disaster Management Coordination Agency.

The collapse sent bursts of volcanic material sweeping into the abandoned former capital of Plymouth, which was buried in a 1997 eruption that killed 19 people, and on into the sea, according to the observatory.

Stewart said the dome of the Soufriere Hills volcano is expected to crumble further, leading to more explosions and lava flows.

The dome has formed and collapsed at least four times in previous years, with the most recent collapse recorded in January 2007, Stewart said. Dozens of people were relocated for about six months during that collapse, White said.

The dome will likely keep growing, "and then one day it will run out of puff," Stewart said.

The volcano, which spewed large columns of ash over the weekend, became active in 1995 and forced the departure of half of the island's inhabitants.