Mexico City - Allegations of negligent construction and poor oversight began to fly on Monday after deadly building collapses during Mexico's earthquake, as hope faded of finding more survivors of a disaster that killed more than 300 people.The most high-profile collapse occurred at a school where 19 children were killed last week - a structure which was built illegally on land reserved for housing, according to local media reports.Mexico City's mayor, the education minister and the top official for the district all traded blame after reports that the Enrique Rebsamen primary school operated using false documents."If confirmed, it would be very serious," Education Minister Aurelio Nuno told TV network Televisa, saying he had ordered an investigation.The government has also come in for criticism from anguished families of people still missing after Tuesday's earthquake.'Lies'"All they tell us are lies," said Anel Jimenez, 42, whose cousin Martin Estrada, a 30-year-old accountant, was inside a seven-storey office building when it collapsed."No one from the government has come to show their face. They just send low-profile officials who always have clean helmets and shiny shoes. They just come to see what they can get out of other people's pain."Rescue workers have now wrapped up their efforts at all but five sites in Mexico City, and the chances of pulling any more survivors from the rubble are dim.But President Enrique Pena Nieto has been careful to insist that authorities will not send in bulldozers to start clean-up until rescuers are absolutely certain there are no more people in the rubble.Twenty-nine people were rescued alive from the building in the first days, and 69 across the city.But since late Friday, only bodies have been recovered.An aftershock that shook Mexico City on Saturday has made the country all the more jittery.And the sense of vulnerability has only been heightened by the fact that Tuesday's earthquake struck on the anniversary of a 1985 quake that killed more than 10 000 people, the worst in Mexican history.