US department store Macy's has said a rogue staffer concealed more than $130m (£103m) in company costs over roughly three years, causing it to delay the release of its latest accounts.

Macy's, also the owner of Bloomingdales and the make-up chain Bluemercury, said it was postponing its quarterly sales update as it investigates the incident.

The person was responsible for tracking expenses related to small package deliveries, the retailer said. It added that it believed the person had acted alone.

Macy's also said the impact was limited and would not affect its payments to other firms.

Macy's said it had discovered an issue related to delivery expenses earlier this month as it started to prepare its financial update.

An investigation and forensic analysis subsequently identified that a "single employee with responsibility for small package delivery expense accounting intentionally made erroneous accounting accrual entries" starting around the end of 2021, Macy's said.

The more than $130m that was concealed was a small fraction of the more than $4.3bn in overall delivery expenses during that time, it added.

Macy's said it expected to give a final report to investors on 11 December. The person allegedly responsible is "no longer employed" at the firm, it said.

It did not respond to a message seeking to confirm the person had been fired.

“At Macy’s, Inc., we promote a culture of ethical conduct," chief executive Tony Spring said.

"While we work diligently to complete the investigation as soon as practicable and ensure this matter is handled appropriately, our colleagues across the company are focused on serving our customers and executing our strategy for a successful holiday season.”

The issue adds to the challenges facing Macy's, the biggest department store chain in the US, which has been struggling with shrinking sales and is heading into an uncertain festive shopping season.

Over the three months to 2 November, sales fell 2.4% from the same period in 2023, as growth at Bloomingdales and Bluemercy was offset by declines at older Macy's locations.