London Drugs is investigating whether personal data was compromised in a cybersecurity incident that prompted the company to close all of its stores across Western Canada until further notice.

A statement from the retailer and pharmacy chain says it will notify "affected individuals" if the probe finds their data was breached.

The company says it's working with third-party cybersecurity experts to securely bring its operations back online after discovering the incident on Sunday.

An earlier statement said there was no reason to believe customer or employee data had been affected by the incident and stores had been closed "out of an abundance of caution."

The Richmond, B.C.-based company says its phone lines have also been temporarily taken offline, but staff are available in person at London Drugs locations to support customers with urgent pharmacy needs.

President Clint Mahlman says in the latest statement that the company's priority is fully restoring operations as soon as possible.

"We appreciate everyone's patience and support during this very difficult time and will provide updates as available."

There are more than 80 London Drugs locations across Alberta, Saskatchewan, Manitoba and B.C.

Canada Post confirmed Monday that offices inside the stores are affected by the closure, but said customers can still collect parcels waiting for them.

Over the last two years, Giant Tiger Stores Ltd., Indigo Books & Music, the LCBO, the Toronto Public Library, the Nova Scotia government and the City of Hamilton in Ontario have also fallen victim to cyber incidents.