Pictures: Mexican volcano Popocatepetl spews ash and smoke as authorities urge caution

Incandescent materials, ash and smoke are spewed from the Popocatepetl volcano as seen from the San Nicolas de los Ranchos community, state of Puebla, Mexico.

The volcano spewed more gas and ash into the sky on Tuesday as authorities maintained their warning level at one step below red alert. | Above: Residents chat on a street covered in volcanic ashes while the Popocatepetl volcano spews a column of steam and ashes.

Dozens of shelters have been opened near Popocatepetl - located around 70 kilometers from Mexico City - which has seen various periods of increased activity since awakening from decades-long slumber in 1994. | Above: Soldiers sweep the ashes from the streets in the village of Santiago Xalitzintla in Puebla state.

The government is monitoring Popocatepetl "day and night," President Andres Manuel Lopez Obrador said after the volcano put on another fiery show overnight.

The President said the volcano's activity had decreased slightly since the alert level was raised on Sunday, helping to calm nerves in nearby towns and villages that have been covered with ash. | Above: View of a car covered with ashes from the volcano in the village of Santiago Xalitzintla in Puebla state.

"Last night I slept a little better because the other three days my house's windows and door vibrated," said Francisca de los Santos, a 56-year-old living in a town close to the volcano. | Above: A soldier stands at a checkpoint that blocks the access to Paso de Cortes while the Popocatepetl volcano spews a column of steam and ashes.

Mexico's National Center for Prevention of Disasters said that over the previous 24 hours, 22 volcanic exhalations of water vapor, volcanic gasses and ash had been detected, along with two explosions.

Roughly 25 million people live within a 100-kilometer radius of Popocatepetl, the second tallest volcano in Mexico, rising nearly 5,500 meters above sea level. | Above: A map with evacuation routes is seen in the village of Santiago Xalitzintla in Puebla state.

Incandescent materials, ash and smoke are spewed from the Popocatepetl volcano as seen from the San Nicolas de los Ranchos community, state of Puebla, Mexico.

The increase in the alert level on Sunday to "yellow phase three" came a day after two Mexico City airports temporarily halted operations due to falling ash. | Above: Residents line up to receive a protection kit in case of ash fall in the village of Santiago Xalitzintla in Puebla state.

A resident sweeps a street covered in volcanic ashes from the Popocatepetl volcano which spewed a column of steam and ashes, in San Nicolas de los Ranchos, in Puebla state.

The next level, a red alert, would trigger mandatory evacuations in communities near the volcano, whose name means "smoking mountain" in the indigenous Nahuatl language.