Residents at the foot of Mexico's Popocatepetl volcano no longer sleep soundly since the towering mountain roared back into action over a week ago, spewing out a hail of rocks, steam and ashes.

"We close our eyes, but we don't sleep much. In the past, there was only smoke but this time it's stronger," said Francisco Jimenez, who lives in the nearby town of Xalitzintla in central Mexico, 55 kilometers (35 miles) from Mexico City.

The volcano, Mexico's second highest peak at 5,452 meters (17,887 feet), started rumbling and spurting high clouds of ash and steam on April 13, provoking the authorities to raise the alert to level five on a seven-point scale.

The alert extended a security cordon around the volcano but stopped short of starting evacuations of some 685,000 residents from nearby communities.

Over the weekend, residents watched as Popocatepetl, which means "smoking mountain" in the indigenous Nahuatl language, lived up to its name, spouting glowing rocks and shaking the ground beneath their feet.

"When we went out to see, my son cried: 'We have to leave!' We were ready to leave for Mexico City but then it calmed down a bit," said 67-year-old Leopolda Perez of Xalitzintla.

Authorities from the National Center of Disaster Prevention maintained their alert level and said Monday that the volcano remains at a "relative calm" state.

After moderate activity during most of the 20th century, Popocatepetl registered more intense rumblings from 1994, with the strongest in December 2000, when nearby communities were evacuated.

Juan Carlos Salazar, head of civil protection for the central state of Puebla, said that while many people thought lava was now coming out of the volcano, the crater was only spewing glowing rocks, with no risk to the population.

Popocatepetl is an explosive volcano that can suddenly erupt at tremendous force, thrusting out rocks and ashes at large distances. That kind of volcano can be more dangerous than those releasing only flowing lava.

Residents say they are used to the permanent threat of the volcano, which they affectionately nickname "Don Gregorio" or "Don Goyo," but many say the new activity makes them nervous again.

"We've been watching out for many nights, waiting to see what happens," said Gabino Santibanez, mayor of San Pedro Benito Juarez, a small town only nine kilometers (six miles) from the glowing crater.

Locals said that most frightening was the unusual rumbling coming from the volcano, which many compared to an aircraft turbine.

"We've never heard a noise like it," said Maximiliano Grajales.

Some 4.5 million people live on the outskirts of the volcano, which lies at the crossroads of the states of Puebla, Morelos and Mexico.

Officials in the area have prepared temporary shelters for possible evacuations and even taken stock of livestock, in case of possible theft.

"Some people won't want to leave because of their animals. Thieves pillaged houses during the 2000 evacuation," Grajales said.

Some now wear face masks to protect their lungs from falling ashes as Don Goyo rumbles and smokes nearby.