Three people have been arrested in connection with the case.
A video of the mother-of-eight sparked massive anger online when it emerged two weeks ago.
Officials first dismissed trafficking claims, but outraged netizens had kept up pressure, with some making daily calls for investigation.
Many of them also raised suspicions about kidnapping and abuse.
Even the hype around the Beijing Olympics has failed to distract people from the issue - a Weibo topic on the woman's plight has received more than 3bn views since the news first emerged.
