Rumbling Volcano Giving Mexico Jitters Popocatepetl may be ready to blow By Mary Papenfuss, Newser User Posted Apr 18, 2012 2:59 AM CDT Updated Apr 18, 2012 3:06 AM CDT 11 comments Comments A plume of steam rises from the Popocatepetl volcano seen from the city of Puebla, Mexico, over the weekend. (AP Photo/Joel Merino) (Newser) – Officials are so uneasy about the rumblings of the now-glowing Popocatepetl volcano near Mexico City that they've shut down nearby schools, and warned travelers to stay away. Eight low-intensity "exhalations" and a 40-minute tremor from the shuddering volcano have been measured by Mexico's National Center for the Prevention of Disasters, reports CNN. The volcano threat has been raised to level 5 out of a possible 7, meaning there's a high probability of some kind of major activity, according to AP. A lava dome is building in the volcano, and Popocatepetl could experience "significant explosions of growing intensity that hurl incandescent rocks significant distances," large ash showers, and lava flows down the volcano's flanks, the center warned. 'El Popo,' which can be seen by Mexico City's 19 million residents on a clear day, is the highest peak in the nation, and last had a major eruption in 2000.