A series of explosions rocked Ecuador's Tungurahua volcano, spewing columns of ash into the air that reached as far as Quito.
Ash fall from the plumes was reported up to 130 kilometers (80 miles) north in the Ecuadoran capital, authorities said.
"There were five explosions of a moderate to large size, which sounded like heavy gunfire for several miles," director of the Geophysical Institute Mario Ruiz told the Gama TV channel.
Tungurahua, which in the Quechua language means "throat of fire," has been erupting since 1999.
Located in central Tungurahua province, it came rumbling to life again on Saturday, prompting the evacuation of hundreds of people from nearby villages.
Wind currents were carrying the ash in a northerly direction on Monday, but on Sunday ash fell as far south as the province of Loja, which borders Peru.
"Most volcanic ash is suspended in the atmosphere south of Quito," the National Institute of Meteorology and Hydrology said on Twitter Monday, as the country's Emergency Operations Committee met.
Ash fall was reported in multiple Tungurahua towns, security service ECU-911 said on its Twitter account, adding that seismic activity was "high."
Authorities have not reported any casualties or damage.
Authorities declared an emergency in high-risk areas in Tungurahua and Chimborazo provinces after Saturday's "significant activity."
Multiple villages are located in the vicinity of the volcano, which stands at 5,029 meters (16,500 feet).
The volcano took its greatest toll in 2006, when a Chimborazo village was destroyed by lava, killing six people.