Eastern European online bookmaker Favbet says a competitor was behind an online attack on the company’s website over the Christmas holiday.

On Christmas Day, Favbet customers received emails from the site informing them that unscheduled “maintenance” was responsible for their inability to access the site for the previous few days. However, the message offered no timeline for when this maintenance would end and the site remained offline for several more days.

In an interview with Russian betting affiliate Bookmakersrating.ru, Favbet COO Sergei Efimenko said the site came under attack by unknown hackers while the majority of the company’s staff was celebrating the holidays at a corporate event.

Efimenko said that within hours of the attack’s launch, the attackers had “destroyed not only the main, but the backup database.” Efimenko said only a “well-built system of protection and resources” that were unknown to the attackers helped the site withstand the attack.