The southern part of Mexico City was put on debris alert after an eruption at the volcano Popocatepetl.
A plume of ash spewed 1,200m into the air on Wednesday morning, according to Mexico's disaster prevention agency, prompting authorities to warn nearby residents.
A live feed from the scene shows clouds still billowing from the summit and spreading across the sky.
People were told to cover their mouths and noses with damp handkerchiefs in boroughs of the city including Coyoacan, Magdalena Contreras, Tlalpan, Tlahuac and Iztapalapa, according to local press.
Authorities are now watching the volcano, which stands at 5,426m, for further unusual activity.
Popocatepetl is the second highest peak in Mexico and lies 73km southeast of Mexico City.
