A preliminary investigation into Wednesday's accident, in which a crane collapsed and killed two workers, indicated that damage was confined to the concourse area and did not affect the stands - which could have taken longer to fix.
The damaged concourse area took about 35 days to build, and previous experience suggests it will take about twice that time to clear the wreckage and rebuild, the source said. If work resumes on Monday, as the builders believe it will, that puts the completion date in early February.
The source, who spoke on condition of anonymity because the probe into the accident is sensitive and ongoing, expressed "high confidence" in the timeline but said it is subject to change pending further investigation by local authorities.
"The reconstruction is not a difficult thing to do," the source said. "Everyone is mourning the workers, but calm about the construction itself."
If proven true, the news would be a relief for Brazil's troubled efforts to get stadiums and other key infrastructure ready on time before the global soccer tournament opens in Sao Paulo on June 12.
World soccer body FIFA has said that all of the stadiums to be used for the event must be finished by the end of December.
The source said, however, that FIFA has always been quietly willing to extend the deadline for the Sao Paulo facility - called Arena Corinthians - by a few months if necessary because construction there started a year later than at other stadiums.
"The timeline needed to open the stadium is guaranteed," the source said.
A spokesman for Odebrecht SA, the conglomerate building the stadium, declined comment. Andres Sanchez, a former president of the Corinthians soccer club who is overseeing construction, did not answer phone calls or text messages.
A FIFA spokeswoman told Reuters by email earlier on Thursday that it was "premature" to gauge how long the accident could delay the stadium's opening until next week at the earliest.
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