The 16,48-foot volcano 84 miles southeast of Quito has been active since 1999.
Mercedes Taipe of Ecuador's Geophysics Institute told the Associated Press the "moderate to strong" eruption is spewing a column of vapor and ash up to 2.5 miles into the sky.
She said Tuesday that a half a dozen villages are being showered in ash. She had no immediate estimate on economic damage to local farming.
Volcano Discovery reports that scientists on an overflight observed "strombolian activity" from the inner summit crater, which has filled with fresh lava. But by Wednesday evening, tremor and seismic activity had decreased a bit again. Strombolian activity, named after the island off Sicily, refers to small but constant eruptions.
On Tuesday, there were 16 large explosions producing strong cannon-shot noises heard in villages near the volcano, TruthDive reports.
In July and August of 2006, eruptions of Tungurahua killed at least four people, left two missing and forced the evacuation of thousands.