According to the Wall Street Journal, the Justice Department is ramping up its investigation into Google, focusing heavily on the company’s ad tools.

According to the report, the DOJ has increasingly been directing its questions—both of competitors and Google executives—toward “how Google’s third-party advertising business interacts with publishers and advertisers.”

At the heart of the issue is the fact that Google essentially controls the entire process, resulting in its ad software being the dominant player at every stage of the relationship between online publishers and advertisers. Google reinforced that even more in recent years with two key decisions, according to the WSJ. The first was when it integrated “its ad server, the leading tool for websites to put ad space up for sale, with its ad exchange, the industry’s largest digital ad marketplace. The second move was Google’s decision to require advertisers to use its own tools to buy ad space on YouTube.”

Competitors have alleged that Google’s tying their services together gives the company an unfair and anticompetitive edge, making it impossible to compete with Google on merit alone.

At least one rival is pleased with the direction the questioning is going. Michael Nevins, chief marketing officer of Smart AdServer told the WSJ: “They are zooming in on the right topics, and that’s a good thing.”