The inspection arm of the United States Postal Service said Wednesday that it is launching an investigation into delivery delays and other issues across the entire Minnesota and North Dakota postal district — on the same day the agency released audit reports detailing widespread problems at four east metro post office facilities.

The USPS Office of Inspector General's audits, which were prompted by pressure from U.S. Rep. Angie Craig and south metro residents' reports of "poor delivery performance" in recent months, found issues with delayed mail delivery, incorrectly scanned packages and building conditions at each site.

"Today was a major development," Craig said in an interview following the release of the audits and announcement of the planned statewide review. "The results of the investigations prove that my constituents were right."

The audit reports relate to the Eagan and Apple Valley post offices, the New Brighton carrier annex and the St. Paul distribution center, located in Eagan. The USPS Office of Inspector General completed the audits from November through January.

Craig said she was notified Wednesday morning by the Office of the Inspector General that the agency will complete a larger investigation of post offices in the region, with a report expected in late April. That move comes days after Minnesota members of the U.S. House of Representatives called for a statewide investigation of post office problems. U.S. Sens. Amy Klobuchar and Tina Smith also called for a statewide inspection in December.

Recommendations for improvements at the Eagan, Apple Valley, New Brighton and St. Paul distribution facilities will be included in the report coming in April, Craig said.

Craig noted that the Minnesota-North Dakota postal district ranks among the 10 worst-performing districts nationwide for first-class mail performance, and that thousands of her constituents have been dealing with no mail for days at a time, lost mail or "egregiously slow delivery." Postal workers have said they're told to prioritize package delivery over first-class mail, she said, and some post offices have turned off phone lines to avoid dealing with residents' questions and concerns.

"The USPS has been telling me for the past year that things are on track," she said. "My constituents have been telling me for the past year that their mail has been coming every three, five or eight days."

Craig noted that the USPS audits indicated there were more than a hundred thousand pieces of delayed mail in Eagan and Apple Valley combined — New Brighton is not included in her congressional district — along with "inadequate resources for postal workers" and "persistent mail security issues." The report documented that postal workers were asked to deliver packages before getting to regular mail, she said.

The reports detail deficiencies in USPS operations. On one November day, for example, investigators noted more than 53,000 "delayed mailpieces" at the Eagan post office.

In Apple Valley, 223 packages were scanned incorrectly over a recent three-month period. A physical inspection found damage to concrete outside, causing a tripping hazard, five unmounted fire extinguishers, a loose railing and damaged drywall.

In New Brighton, two of the 37 mail carriers employed there had reported to work for fewer than nine weeks of a 12-week period, but managers hadn't removed them from delivery assignments. Also noted: an instance where a carrier scanned a package as "delivered" — 3 miles away from where it was supposed to go.

At the St. Paul distribution center, investigators found more than 56,000 delayed letters and other mail items over three days in November. The report said the facility's managers had not adequately staffed the units sorting the mail in time for it to be sent out for delivery.

In each of these instances — and for nearly every issue detailed in the report — management was blamed for oversights.

"[These reports are] clear that management of these facilities and this region is the issue," Craig said.

Each of the four audit reports included a written response from Angela Bye, manager of the Minnesota-North Dakota district, or John Darden, division director of Midwest logistics operations. Both largely agreed with the reports' findings, but Bye identified several instances where the total number of mail scanning problems were insignificant given the large number of packages scanned.

In a statement, Klobuchar called the audit findings "deeply concerning, but not surprising" and said she's glad officials are expanding the investigation statewide.

"Minnesotans rely on the Postal Service to receive their paychecks, prescriptions, and more, but I have gotten reports about delays and issues with mail delivery across the state," said Klobuchar, adding, "We need answers so we can find solutions that work."