In recent months, a manager and several employees said, unsorted mail sat for weeks in overflowing bins on the plant floor or was stuffed into trailers in the parking lot and - in some cases - even shipped in desperation to other distribution plants, from where it often returned for sorting days later.
In some cases, the mail was destroyed, the employees said.
The postal employees and a manager spoke to the Daily News on condition of anonymity, saying they feared retribution if they spoke publicly.
The workers interviewed by the Daily News said the severe staffing shortages were the result of a year-long overtime ban.
A complaint filed by the postal workers' union with the USPS Office of Inspector General alleges that a senior manager and others ordered clerks to falsify the daily mail report, undercounting the volume by hundreds of thousands of pieces of mail, to save costs and overtime.
"The mail is here. You'd have to be blind not to see it," said a veteran employee.
"What really hurts me is the [possibility] that these [fake] numbers were used in determining how many employees were outsourced in Philadelphia," said Byron Murtaugh, APWU assistant clerk craft director and a 20-year postal employee.
In August, USPS officials here announced that 162 employees are to be transferred in January.
A lead senior manager and other managers received performance bonuses that were "fraudulently obtained, through the systematic falsification of official government reports, the diversion of mail, and the destruction of mail," the union complaint alleged.