An explosion at the crater of Mexico's Popocatepetl stratovolcano has hurled incandescent rock about 1 ½ mile (2.5 kilometers) down its slopes and sent ash into the night sky near the nation's capital.

The Mexican government disaster agency says ash was expected to fall on towns near the crater following the outburst at 9:38 p.m. (11:38 p.m. EST) Monday.

The 17,797-foot (5,426-meter) volcano has been particularly active in recent months, several times spewing out sprays of hot rock and towering clouds of ash

Some 25 million people live within about 60 miles (100 kilometers) of the mountain's crater.