Dutch hotel reservation website Booking.com is facing an antitrust probe by a Spanish antitrust watchdog over accusations of potential unfair competition practices which affected hotels and rival travel agencies within Spain.

In a statement released by the regulator, it announced the investigation arose from a pair of complaints filed by the Spanish Association of Hotel Managers (AEDH) and the Madrid Hotel Business Association. It said there were “reasonable grounds” to the accusation that Booking.com may have run afoul of Spanish antitrust laws as well as Article 102 of the Treaty on the Functioning of the European Union, which specifies companies may not abuse a dominant market position.

AEDH President Manuel Vegas said in an interview that, “What we really want is those practices to end.”

The investigation by the watchdog will take 18 months. Bookings.com could face fines of  €100,000 (nearly $98,000) to more than €10 million ($9.8 million) per infringement if they are found guilty of violations.

The complaints alleged that the company had imposed unfair conditions on Spanish hotels and its policies could have led to exclusionary effects on competitor travel agencies and other online sales channels. The watchdog also alleged it may also have exploited Spanish hotels which were dependent upon it to acquire bookings.

Booking.com said it would cooperate fully with the investigation and stood ready to answer any questions the watchdog had regarding its business in Spain.