The Mexican authorities have raised the number of casualties to 224 after a 7.1-magnitude earthquake shook the centre of the country, an official said.The emergency services were carrying out rescue operations in the areas affected in the Tuesday disaster, Efe news reported.Mexico's National Coordinator for Civil Protection, Luis Felipe Puente, confirming the toll gave the break-up of various areas -- 64 in Morelos, 36 here, 29 in Puebla, nine in the State of Mexico and one in Guerrero.As night fell, thousands of troops were working in the dozens of dilapidated buildings here.On Monterey Street, near the Miguel Aleman Viaduct one of the city's main thoroughfares, a building with at least four floors has collapsed completely.At least a hundred soldiers, fire-fighters and civil defence officers using shovels and picks and buckets were remove the debris, working arduously against the clock to get the alive out from under the rubble.The Dog Squads were also pressed into service."We pull out debris and work in a line, and when they ask you to be quiet, you remain silent. If applause is heard, we start to get the person out", a young man explained.Emergency teams were attempting to rescue people trapped in collapsed buildings here. Traffic chaos has made it difficult for ambulances to get through as fears of new quakes loom on people's mind.Director of the National Centre for Disaster Prevention (Cenapred), Carlos Valdes, ruled out the possibility of strong aftershocks due to the depth of the epicentre at 57 km. So far there have only been two, the largest one is of 3.3-magnitudes, he said.The Federal Electricity Commission (CFE) reported that 3.8 million residents were without electricity, after it was cut off as a prevention measure.Tuesday's quake coincided with the 32nd anniversary of the 1985 earthquake that claimed thousands of lives.Tuesday's quake also follows the 8.2-magnitude quake on September 7, that killed 98. It was considered the strongest since 1932.