Construction crews moved with cranes and bulldozers today into the crumpled ruins of the Edificio Nuevo Leon, the largest of the scores of government-owned apartment buildings demolished by last week's earthquake and the structure whose collapse is believed responsible for the largest single loss of life.

Erected in 1962, before the city's 1976 adoption of a stricter antiquake building code, the building is at the center of both domestic controversy about allegedly irresponsible governmental construction practices and the growing international interest in the Mexico City earthquake's lessons for other quake-prone cities.

The last of the fewer than 30 persons who emerged alive from the shattered apartments was extricated from the rubble late Monday. Two of the building's three 90-apartment units were knocked on their backs by the earthquake. It is not known how many of the estimated 1,200 residents were inside at the time, said Francisco Melendes, a borough government spokesman at the site today.

As recently as last month, Nuevo Leon residents complained to authorities that cracks left in its foundation by previous tremors appeared to be widening. Government inspectors examined the building and pronounced it safe, said representatives of tenant associations, who asked Mexico's Congress today to conduct an inquest into possible civil and criminal violations of the city's earlier construction code. It was drafted after Mexico's last big earthquake in 1957, and once was considered a model for such legislation.

But the Edificio Nuevo Leon's collapse may have been due less to structural flaws than to the combination of its high-rise design and its location atop the city's muddy subsoil, a partially dried former lakebed, a U.S. anti-earthquake engineering specialist suggested as he toured the site today.

Seismically, Mexico City has "very peculiar characteristics," explained Mete Sozen, a University of Illinois structural engineer. Its soft substructure "amplifies the energy" of earthquakes, he said, often making them far stronger than their force on the Richter scale would indicate.

"The ground here Thursday was moving back and forth by about 20 centimeters every two seconds, much more slowly than it would in an earthquake in a city like Los Angeles or San Francisco," said Sozen, one of five members of a special research team sent here Saturday by the U.S. National Academy of Sciences and the San Francisco-based Earthquake Emergency Research Institute. That steady swaying motion accounted for the fact that squat, stone Spanish colonial buildings "that would have crumbled to the ground" in California survived here Thursday almost unscathed, he said.

"I haven't seen evidence of faulty construction," but the Nuevo Leon building could have been doomed simply by its narrow, shoebox-like shape and the unusually violent, "almost liquid" motion of the soil on which it stood, Sozen said.

As fumigation teams today sprayed disinfectants on the toppled building, attention began to turn to the condition of the remaining buildings in the huge Tlatelolco apartment block, consisting of 102 buildings and 80,000 residents, that is Mexico's largest public housing complex.

Of immediate concern to Tlatelolco residents is the fate of a dozen buildings similar to the Edificio Nuevo Leon that have been evacuated and provisionally condemned. More than 10,000 tenants were evicted and many fear they may remain homeless for weeks or months.

"They shut us out, and they haven't told us anything officially since," complained Augusto Nava. His family, like hundreds of others, moved out of its building and pitched a tarp in the nearby Plaza of the Three Cultures.

The three cultures are those of the Aztecs, represented by a reconstructed temple where one of the last Aztec kings was invested 470 years ago; the Spanish, as seen in a colonial church, and the Mexican culture that emerged from those two strains. The latter is represented by the skyscraper Foreign Ministry.

The plaza was the site of a 1968 massacre in which dozens of leftist demonstraters were killed by anonymous gunmen who, it turned out, were deployed by the Interior Ministry. Today the grassy plaza took on the oddly bucolic air of a campground as bright nylon tents stood next to ancient Aztec walls and volunteer medical workers dispensed oranges and tetanus shots.