The U.S. Department of Justice (DOJ), which launched its investigation into the proposed Ticketmaster/Live Nation merger last month, has asked the two powerhouse companies for more information pertaining to the case. What specific information was requested is unknown.

Since the announcement of the planned, $2.5 billion merger, the deal has drawn intense scrutiny from members of Congress and all aspects of the live entertainment and ticketing industries because the two companies sit atop of those two respective sectors, and they were poised to become business rivals before the merger plan became public.

Though the exact nature of request is unknown, in other unrelated mergers, the DOJ sometimes asks for information on competition, products, prices, innovations, expansions as related to the two businesses over the past few years. Compiling the information can take months.

Opposition to the merger has come from the likes of Bruce Springsteen, Trent Reznor of Nine Inch Nails, and New York Sen. Charles Schumer, who Ticketmaster Chairman Barry Diller said is “grandstanding,” while the famous executive was speaking during a conference call with investors Thursday, March 19.

“This request for additional information from the DOJ is a standard part of the full regulatory process,” the two companies said in a joint statement. “Live Nation and Ticketmaster Entertainment are in the process of gathering information to respond to the second request, and are working cooperatively with the DOJ as it reviews the merger.”

A spokesperson for the DOJ did not return a message seeking comment. Despite the request for more information, the two companies still expect to finalize the deal in the second half of 2009. In addition to federal regulatory approval, the deal also is subject to shareholder and certain third-party approvals.