The Department of Justice (DOJ) will review Google's $400 million purchase of Admeld Inc., an Internet advertising company, to investigate whether the deal had an adverse effect on competition.

The DOJ's investigation coincides with the Federal Trade Commission's (FTC) antitrust investigation of Google's dominance in the search-engine industry.

According to Bloomberg, concurrent antitrust investigations of a company by the two federal agencies are rare.

Google's acquisition of Admeld is expected to secure its position as the leader in the display-advertising market, which is the fastest-growing segment of the Internet advertising market. According to a May 26 report by market research firm International Data Corporation, Google had 14.7 percent of the display-advertising market in the first quarter.