DCF in Beijing: Retained originals of marriage and divorce documents

[syzygy 1]

My wife and I submitted the I-130 petition and I-130a at the Beijing Embassy recently. I had assumed that all Beijing would do would be to check to see if the forms had been properly filled in and the necessary documents and copies had been included. However, they retained the originals of the marriage certificates and divorce certificates (Chinese), and told us that they would be investigating our case, and that we might be asked to provide more evidence to prove the genuineness of our marriage, and might even be interviewed. This was a surprise to me, as I had assumed that sort of thing would only be done by the Guangzhou consulate. My wife had previously been married to another American citizen, and he began the immigration visa process which was not completed. I notice that the new edition of the I-130 petition (p.5, Part 4, #10) does ask "Has anyone else ever filed a petition for the beneficiary?"...which wasn't asked before, if I remember correctly. So evidently the US government is being more careful of such cases...something I have worried about for years. When I asked what the process would involve, I was given a very vague answer...really no answer at all. And I was told that the process might take up to three months to complete before the petition was either accepted and sent on to Guangzhou or denied. Can anyone tell me what Beijing will do as part of its "investigation", and whether it is SOP to retain marriage and divorce documents? I have asked in another thread if I had cause to worry that my wife's previous marriage to another American would cause problems, but didn't receive much response. The fact is that her previous marriage, on the surface at least, does seem sort of shady. Is the retention of the marriage and divorce documents a sign that we will in fact have a problem, or is it just standard procedure? Thanks in advance for your help.