The blast could create an ash cloud bound for Mexico City, which is about 40 miles northwest of the volcano.
The volcano has been restive since last year. The blast was captured on film stretching high into the sky and dumping bits of rock into neighboring areas.
If Popocatepetl continues to erupt, the area will likely be evacuated. Evacuations were planned in mid-May during another active period, but were never enacted.
The volcano is under constant monitoring for activity using cameras, satellites and sensors to track changes in temperature and ground movement.
The volcano is the second-highest volcano in Mexico, and it had its last major eruption in 1947. It was dormant from the 1950s until 1994, when it began to erupt intermittently. A large eruption in December 2000 caused damage, but evacuations and monitoring kept residents from getting hurt.