As Federal Trade Commission antitrust lawyers try to police vast swaths of the economy with limited resources, they’re making trade-offs. The FTC earlier this year stepped up a long-running investigation into whether a group of major hotels including Hyatt, Hilton and Marriott hurt customers by colluding to stop competing for ad space in Google Search results, according to people familiar with the probe. Then the antitrust agency unexpectedly hit the pause button.

In August, FTC staff told the hotels that although the investigation—whose existence hasn’t previously been reported—would remain open, it would slow down as the agency focused more on reviewing mergers, these people said. The move shows how an M&A boom appears to be stretching the resources of the 1,100-person agency.