SAO PAULO, Brazil — Prosecutors said yesterday they suspect mistakes by a consortium of private builders, rather than heavy rains, caused the collapse of subway station construction site that buried at least seven people.Authorities also warned they may halt work on the station, part of a US$1.4 billion subway line being built in South America’s largest city, as they investigate what caused last Friday’s collapse that killed three people and left four others missing and presumed dead.

“A serious mistake was made, and what we have to do now is determine if it was in the project or in its execution,” said Sao Paulo state Attorney General Rodrigo Pinho.

A 130-foot-wide circular hole lined with concrete gave way without warning, swallowing pedestrians, a minibus driving by the site, and dump trucks being used in the project.

Several nearby homes were damaged and must now be torn down.

Pinho said the consortium’s suggestion that rain played a leading role was “ridiculous” because Sao Paulo typically experiences heavy rain during the South American summer from November through April that all construction companies factor into their building plans.

Earlier yesterday, rescue crews recovered the body of truck driver Franciso Sabino Torres, bringing to three the number of dead retrieved from the crater-like hole left after the site’s collapse.

Authorities were still trying to recover the bodies of four more people thought buried under tons of rubble and debris.

Experts said authorities should also investigate whether there were sufficient government inspections on the construction of the line and whether cost-cutting may have played a role.

“Outside monitoring may have detected engineering flaws that went undetected before the tragedy,” said Waldemar Hachich, a Brazilian engineer who is also vice president of the London-based International Society for Soil Mechanics and Geotechnical Engineering.