Canada’s largest bookstore chain says its website is unavailable following a cybersecurity incident Wednesday.

In a statement posted to Twitter, Indigo said it is working with third-party experts to investigate and resolve the situation.

“We sincerely apologize for any inconvenience this may create for our valuable customers,” the bookstore said. “Our hope is to have our systems back online as soon as possible.”

Indigo initially said on Wednesday afternoon that it was experiencing “technical issues,” and that its website was unavailable.

Indigo said it only accepted cash transactions in stores, as electronic payments could not be processed. The bookstore added it was also not accepting gift cards or returns.

It is unclear if any personal information was compromised during the incident.

“We appreciate your patience as we work hard to resolve this issue,” Indigo said. “We commit to updating our customers as more information becomes available.”