For years, Macy’s Inc. touted its ability to boost profits by cutting delivery costs and trimming other expenses on calls with Wall Street analysts. Then on Monday, the department store chain surprised investors by revealing that those very costs had become the source of an internal investigation into what the company has described as a multimillion-dollar employee plot to manipulate the metrics.

Macy’s says it’s delaying the release of its fiscal third-quarter earnings results after it discovered an up to $154 million accounting-related issue.

The employee "intentionally made erroneous accounting accrual entries" to hide millions of dollars, Macy's said. The error forced the company to delay reporting its third-quarter results.

A former employee intentionally hid expenses totaling as much as $154 million in the company's small package delivery department over a roughly three-year period, Macy's said in a financial disclosure on Monday.