The ash cloud is so severe, it's dusted at least four provinces.
The volcano has calmed since Monday's blow-up, however, moderate explosions are still being witnessed.
No injuries have been reported, but the blast did damage local flower harvests.
Schools were closed in various communities as a precaution and flights were halted near the volcano.
Santiaguito is a crater on the slope of the 3,772 m Santa Maria volcano, located about 200 km northwest of Guatemala City.
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