Alert Level Is Raised in Central Mexico as Volcano Spews Smoke and Ash

An alert level was raised on Sunday for a volcano in Central Mexico that was spewing ash and smoke, prompting officials to close schools and public parks, and to prepare for the possibility of evacuations.

The National Disaster Prevention Center of Mexico said on Sunday that the alert level was being raised to what is known as Phase 3, which is just shy of an evacuation order, for the area around the volcano, Popocatépetl, in the central region of the country.

Laura Velázquez Alzúa, the head of the center, said at a news conference on Sunday that when an alert level is raised to Phase 3, it is possible for a volcano to produce mild to moderate explosions that can hurl fragments of rock, cause ash to fall in surrounding areas, and disrupt air travel. The expulsion of magma is also possible, the center said.

President Andrés Manuel López Obrador of Mexico said at a news conference on Monday morning that he was in contact with federal and local officials about the volcano, adding that it was being monitored constantly.

“We are standing by,” Mr. López Obrador said in Spanish.

The disaster prevention center said that authorities in the area surrounding Popocatépetl were preparing evacuation teams and shelters, and that local and state officials were also planning to tour evacuation routes on Monday.

“We need to be perfectly sure that our evacuation routes and signs are correct,” Ms. Velázquez Alzúa said.

Popocatépetl (pronounced poh-poh-kah-TEH-peh-til), sometimes referred to as a god of rain or the community’s heartbeat, was quiet for decades before it became active in the 1990s. In 2000, a major eruption prompted the evacuation of about 50,000 people from the region. Since then, mild to moderate activity from the volcano has prompted officials to occasionally raise alert levels.

It was unclear on Monday how long this period of raised volcanic activity would continue.

Jessica Ball, a volcanologist with the U.S. Geological Survey, said it is normal for active volcanoes, such as Popocatépetl, to go through cycles of increased activity.

“That is pretty much just part of being an active volcano,” she said. “There’s really no cycle on a human time scale that governs which volcanoes erupt at which time.”

A time-lapse video that the center shared on social media on Monday showed the volcano spewing smoke and ashes in the early morning.

On Monday afternoon, officials suspended operations at Hermanos Serdán International Airport, a small facility in Puebla, because of ash on the runways.

Officials said at a news conference on Sunday that the state of Puebla, which includes a portion of the volcano, had set up 35 shelters with space for up to 22,000 people if evacuations were needed.

Puebla state officials also said on Sunday that, to minimize the risk of exposure to falling ash, several public parks in the area would be closed and schools would hold classes virtually for the time being.

The National Disaster Prevention Center urged residents who live near the volcano to avoid going outdoors as much as possible. Those who do go outside should wear a face mask or cover their nose and mouth with a handkerchief, the center said.

In areas where ash was accumulating, the center said residents should cover water containers to avoid contamination, and sweep the ash and collect it in bags.

The volcano alert level was raised a day after Popocatépetl caused ash to fall from the sky, prompting the temporary closure on Saturday of the two main airports serving Mexico City, about 55 miles northeast of the volcano.

Volcanic ash is particularly dangerous to aircraft, according to the U.S.G.S. Falling ash can interfere with plane radio transmission and navigation systems, it can block fuel nozzles and it can create dangerous conditions on runways that can lead to braking issues.