A North Park resident found his dumpster filled with undelivered mail. View Full Caption Facebook/North Park Neighbors Chicago

NORTH PARK — The U.S. Postal Service says it is investigating how hundreds of pieces of mail ended up in the trash last week.

"The whole neighborhood's mail was in the dumpster," including scores of city sticker renewal notices and "a lot of private mail," said Samuel Tenenbaum of the 60659 ZIP code, who made the discovery on Thursday.

"It's ridiculous," said Tenenbaum, who found the mail in a dumpster in the 3500 block of West Thorndale Avenue. He immediately called police and the Postal Service and shared the discovery on social media, he said.

Three postal employees arrived to cart away the mail, he said.

Patty Wetli explains some of the mystery surrounding the mail dump:

Mark Reynolds, a spokesman for the Postal Service, said the mail found in the dumpster was collected and then "delivered over the weekend." Such dumping of mail "does not happen often," he added.

Reynolds said the Postal Service's Office of the Inspector General conducted an investigation. The Inspector General's Office did not immediately respond to a request for comment.

Tenenbaum said he came across the mail when taking out the trash.

"My dumpster was full with stashed mail — full," he said. "I checked the next dumpster to make sure there was no body inside."

Police arrived after a dispatcher initially told Tenenbaum the junked mail didn't fall under the Chicago Police Department's jurisdiction. Officers investigating the matter were present when three female postal employees drove up in two private cars, according to Tenenbaum.

"The three women started grabbing the mail. The police asked them for ID, and two didn't have any," he said. "No explanation was given, no apologies. They were nasty, giving attitude."

The postal employees "asked us to go away," he said. "They said we weren't allowed to take any pictures," an order neighbors ignored.

"They grabbed the mail as quickly as they could and drove off," he said.

Delay or destruction of mail by a Postal Service employee is punishable by up to five years in prison, according to a U.S. Justice Department news release announcing charges last year against a carrier who allegedly threw more than 1,000 pieces of mail in a Warwick, Rhode Island, dumpster.