The UK's Metropolitan Police is investigating a cyber attack on Marks & Spencer which has seen the retailer face major disruption.
The force confirmed that officers from its cyber crime unit are investigating, amid reports a hacking group known as Scattered Spider may have carried out the attack.
Marks & Spencer initially saw problems with its contactless payments and click and collect orders last week, then on Friday it paused orders through its website and app.
Staff at a key logistics site were told to stay at home due to the continued disruption on Monday, and some stores were left with empty shelves.
The National Cyber Security Centre said it is also working with the retailer "to support their response to a cyber incident". 301236 APR 25
M&S, one of the best known names in British business, stopped taking clothing and home orders through its website and app last Friday following problems with contactless pay and click and collect services over the Easter holiday weekend.
An M&S spokesperson said earlier this week that as part of its "proactive management of the incident" it had taken some its systems temporarily offline.
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"As a result, we currently have pockets of limited availability in some stores. We are working hard to get availability back to normal across the estate," the spokesperson added.
While M&S has not disclosed the nature of the cyber incident, cyber security experts have said the fact that M&S took systems offline suggested it was likely a ransomware-related event.
The spokesperson declined to say when online orders are expected to resume.
The 141-year old M&S, which has about 1,000 stores across Britain, makes around one third of its clothing and home sales online.
Analysts have said a short term profit hit is inevitable.
M&S's food business had been trading well prior to the cyber incident.
Market researcher Kantar said this week that spending on groceries at M&S grew by 14.4% in the 12 weeks to April 20 year-on-year.
