Walmart has warned customers to be on the lookout for “suspicious” cartridge printers.

A spokesperson for the retailer told Business Insider the cartridge printer found on the retailer’s website appeared to be a printer that had been used to create cartridges for other retailers.

“This is a unique and unusual device,” the spokesperson said in an email to Business Insider.

“We are investigating this as part of our ongoing efforts to protect our customers.”

It was unclear whether the printer had been connected to other Walmart websites or a third party, but it could have been a remote access tool, such as one from the cloud.

It is unclear what specific cartridge printers are being used in the attack, but they could be used by the retailer to make more than one cartridge at a time, Business Insider reported.

The cartridge printer has been linked to other retailers that have been targeted in the past, including Target, Amazon, Best Buy and Walmart.

Walmart told Business Insights that the printer was “not an employee-operated product”.

“It was a new, unknown and unique type of printer,” the retailer said in a statement.

“As a precautionary measure, customers should check for suspicious activity before purchasing from our stores.”

The company said it was investigating the incident and is “working to identify the source of the attack and to provide an update”.

The retailer’s security team is working with law enforcement to identify any potential criminals responsible.