Adjustment of Status - I-485

So I had my interview 3 weeks ago in los angeles. The interview went good. Officer first asked questions about the I-130 then moved on to questions about I-485. My husband had already a petition from his brother way back from 2001 so we are applying for adjustment under INA 245(i). Since we did not have any documents/notices about that, we submitted a FOIA to get it. We were provided a printout from their system where it indicates that the petition was submitted before April 30, 2001 and approvable when filed. So in the interview, the officer said that he had to verify the brother's petition before making a decision. It's been 3 weeks and nothing. Does anybody here know how long this would take approximately? Seems like the officer is requesting the petition from some other office. Thanks!!!