H4 blue slip stating additional administrative processing required

My wife attended dependent visa interview with channai US consulate yesrerday. She has been issued with 221 g form stating " your application requires additional administrative processing before final decision can be made" . They have not asked for any documents and her passport is taken by them. My wife has been told that they were unable to get my h1b petition details in their system. What would be the issue . how long will it take to process this ?.

Only reason for not finding my extended petition info could be that I received my petition document 3 weeks back and it was through premium processing.

They look at PIMS to get petition info. If the petition was approved but not updated in PIMS, then that could cause the delay. Talk to your attorney to see if they can follow-up on PIMS update.