Mexico City Mayor Miguel Angel Mancera Monday activated Operation Popocatepetl, a contingency plan to prepare for the possibility of a major eruption from the active volcano located southeast of Mexico's capital.

The Popocatepetl Volcano has been increasingly active, and could spew enough ash and glowing rocks to force the evacuation of thousands of people living in nearby communities in the central states of Puebla, Morelos, Mexico State and Mexico City.

Over the weekend, "Popo," as the volcano is commonly known, showed signs of greater activity, spewing steam, gas and ash into the sky, as well as some incandescent rocks and earth, leading authorities to elevate the alarm level to yellow phase 3, one stage away from a red alert, which would instigate evacuations.

Mexico City's Civil Protection Secretariat head Fausto Lugo Garcia said the contingency plan targets communities most at risk, including those in the capital's districts of Tlahuac, Milpa Alta, Xochimilco, Iztapalapa and Venustiano Carranza, where the city's Benito Juarez International Airport is located.

Different city departments are taking part in Operation Popocatepetl, which calls for the sweeping and collection of volcanic ash, and the mobilisation of city police to safeguard homes against looters, among other actions, Lugo told reporters.

He added evacuations will only be carried out in case of a major emergency.

Should the volcano spew significant amounts of ash into the atmosphere, city residents remain indoors, in their homes, cars or offices, Lugo recommended, saying if they need to go out, they should cover their eyes, nose and mouth with a damp cloth.

During a yellow phase 3, people should avoid exercising outdoors, cover their pet's food, and wash fruits and vegetables well.

The alarm also restricts vehicle traffic within a 12-kilometre radius of the volcano, which towers 5,500 metres above sea level.