The office is investigating whether Expedia conspired with Marriott International, Hilton Worldwide and other hotel companies to manipulate search advertising on Google, according to papers filed in state court in Utah last week. Other states have joined the investigation, the office said in the filing.

The allegations were raised in a lawsuit filed in December by TravelPass Group, a Utah-based company that sells hotel room inventory through Google search ads. It accuses hotel chains and Expedia of restricting competition to buy those ads and reducing consumer choice.