The Justice Department has reportedly opened a formal antitrust investigation of the multimillion-dollar Microsoft-escaping deal for Google to provide advertising to Yahoo’s search engine, with a demand for documents going out to other than the immediate parties, not just the voluntary collection of information Yahoo and Google were prepared to supply.

According to the Washington Post, “a formal investigation signals that the department may have found some cause for concern.” It’s not the usual routine.

Yahoo claims it’s not worried.

It’s unclear how long the review will really take. It could be more than the three-and-a-half months the pair allotted to the exercise or until the end of September. Heck, it could take into the next administration, a box even Pandora might be reluctant to open.