The national emergency commission has imposed a restricted area with a five-kilometer radius of the Turrialba volcano.
The agency, the Comisión Nacional de Prevención de Riesgos y Atención de Emergencias, said that the restriction would apply for at least week while scientists conduct studies and evaluations of the mountain.
Eruptions have increased their frequency, and there were more Monday. Juan Santamaría airport was closed for about three hours while ash was cleared from the runways. A half dozen flights were canceled and others were delayed. There were some dozen eruptions Sunday, but the winds carried the ash more to the west.
The Observatorio Vulcanológico y Sismológico of the Universidad Nacional and the Red Sismológica Nacional of the Universidad de Costa Rica have staffers at the scene. In addition, activity in the mountain is being monitored acoustically.
The restriction mainly applied to visitors and tourists. There still are persons and livestock near the volcano. The emergency commission has plans for quick evacuations, if necessary.