Rescue crews Tuesday resumed their efforts at a collapsed Sao Paulo subway station construction site to retrieve a minibus trapped under tons of earth and rubble for three days.

Relatives of the four people believed trapped in the bus and a truck driver also feared buried, said they had given up hope that their loved ones were alive. They were outraged at an earlier decision to halt the retrieval effort.

Aerial view of the hole where a subway station under construction collapsed in Sao Paulo on Jan. 15.
(Victor R. Caivano/AP)

After a second structural analysis showed the crater-shaped site was unlikely to collapse further, workers restarted the search Tuesday, Marcio Pellegrini, an engineer working with the consortium overseeing the subway's construction, told the O Globo newspaper's website.

Thais Gomes, whose husband Adriano Silva, 22, worked as a fare collector on the buried minibus, was quoted by O Globo as saying, "We know that my husband is dead but we want him pulled out of there. He's not a pauper."

So far, rescuers have recovered the bodies of two women, including a 75-year-old who was walking near the site when its concrete walls collapsed Friday.

In addition to Silva, three other people were believed to have been inside the minibus, which is entombed some 90 metres below ground level. A truck driver was also thought to be buried.

"The possibility of finding survivors after a tragedy like this is what motivates rescue workers," civil defence coordinator Jair Paca de Lima told the Associated Press. "But unfortunately I have to say that the chances of finding survivors is minimal."

Engineering flaw possible

Workers tunnelled below the minibus to reach it and approached from above with heavy machinery. They had to work slowly from above to prevent another collapse, and the situation below was too precarious to get close enough to the bus to extract it.

Construction companies said unusually heavy rains played a major role in the collapse of a huge hole being dug for a subway station.

But Deputy Gov. Alberto Goldman said Monday he believed a "major engineering flaw" also helped produce the crater, which swallowed dump trucks, ripped apart subterranean concrete walls and damaged several homes that must now be torn down.

Witnesses said the 40-metre-wide hole lined with concrete gave way without warning, injuring several construction workers. More than 100 people living near the site were evacuated from the area because a 45-tonne crane might fall.

The union representing subway construction workers said at least 10 other accidents have occurred in construction of the subway line, but Friday's collapse was the worst in the system's 32-year history. The station is one of 11 being built along a new 13-kilometre Yellow Line, a $1.6-billion project expected to be concluded in 2012.