The shallow, 7.1 magnitude quake killed at least 225 people in total and caused major damage across states in the centre of the country.
Desperate searches for survivors under the rubble are continuing.
Hopes rose at the school when a girl was located alive and a delicate operation to rescue her is under way.
Dozens of buildings collapsed across the country, including several churches where worshippers were killed.
Families with young children could be seen sleeping outside their homes in the street in the capital overnight.
The tremor struck shortly after many people had taken part in an earthquake drill, exactly 32 years after another quake killed thousands in the capital.
Mexico is prone to earthquakes and earlier this month an 8.1 magnitude tremor in the south left at least 90 people dead.
Though it struck a similar region, Tuesday's earthquake does not appear to be connected with the quake on 7 September, which was at least 30 times more energetic.