United States Postal Service carrier Henrietta Dixon sorts mail to be delivered before she sets out on her route in Philadelphia in this file photo. Portland's postal workers union has accused the Portland postmaster of prioritizing Amazon over other mail. Credit: Matt Rourke | AP

Portland’s postmaster is being accused of intentionally delaying the delivery of mail in favor of prioritizing the delivery of Amazon packages ― a possible violation of federal law.

The complaint accuses Postmaster James Thornton of instructing clerks to sort Amazon packages first. Filed by Mark Seitz, president of the Maine State Association of Letter Carriers and the National Association of Letter Carriers Local 92, his allegation was corroborated by two other letter carriers who said they wished to remain anonymous for fear of retribution, the Portland Press Herald reported. The complaint was filed with the U.S. Postal Service Office of Inspector General on July 13.

The U.S. Postal Service is already under fire for repeated budget deficits and its need to be financially viable. It is also struggling to handle a surge in online shopping deliveries while trying to cut costs by limiting overtime and reducing extra trips, both cuts ordered by the new postmaster general, Louis DeJoy.

Willful delay of the mail is a criminal offense under federal law that carries a sentence of up to five years imprisonment or a fine.