Stop & Shop’s website and mobile app were offline Monday night as its parent company, Ahold Delhaize, responded to a cybersecurity incident affecting its network. Ahold Delhaize said Monday it was investigating a “security issue within its network” and had taken some systems offline as a precaution while working to assess and contain the problem. The company did not disclose the incident’s extent or identify what information or systems may have been affected. Stop & Shop’s online services displayed a maintenance notice. The company said its stores, pharmacies and gas stations were operating as usual and that it was working to restore service. Customers with online orders that could not be completed were told they would receive refunds. The incident also affected Hannaford and Giant Food, which, like Stop & Shop, are owned by Ahold Delhaize. The company said its response was intended to protect customers, employees and business partners, and apologized for the disruption. The outage left customers unable to use Stop & Shop’s digital services for online shopping while in-store operations continued. Ahold Delhaize had not provided further details about the cause or potential impact of the security issue as of Monday night.