A cloud of ash that climbed 4-kilometres into the air from Tungurahua volcano has affected a third of Ecuador's provinces and forced the suspension of classes at some schools after temporarily closing a regional airport.
A series of 10 powerful cannon-like blasts shook the 5023-metre-high (16,480-foot) volcano overnight. Tungurahua is nearly 140km south of Quito.
Fernanda Naranjo of Ecuador's geophysics institute said there have been no pyroclastic flow - fast-moving, super-hot fluidised masses of rock fragments and gases - since Saturday (local time).
One such flow halted less than a mile from a highway, according to a bulletin posted on the institute's website. But none has reached villages, where residents have been evacuating their homes during the night time, then returning during the day. The volcano resumed erupting late last week after being quiet since October.
In Monday's bulletin, the institute said it was likely that Tungurahua would continue to experience explosions and produce small and moderate pyroclastic flows. It also said continued adverse health effects and more disruptions of air travel were possible.
On Sunday, ash from Tungurahua forced the closure for several hours Sunday of the Mariscal Lamar airport in Cuenca, Ecuador's third-largest city.
The government called for voluntary evacuations of hundreds of people living near Tungurahua, officials distributed masks to protect them against the inhalation of ash.
Tungurahua has been erupting sporadically since 1999. In 2006, a pyroclastic cloud killed four people and left two missing.