Two men illegally cut down 400 trees near the historic Susie Nichols Cabin in Ozark National Scenic Riverways. Inset: historic photo or Susie Nichols on her horse "Ol' Don" in front of her cabin./NPS

Editor's note: This updates to explain that the men were logging on lands outside the park and encroached into it, clarifies that length of the investigation was due to legal negotiations.

Two men who accidentally logged some 400 trees from across 31 acres of Ozark National Scenic Riverways in Missouri have paid restitution of more than $52,000 to the federal government, which declined to seek criminal charges as the men exhibited no criminal intent.

The total bill paid by the men was $52,469, according to a release from the National Park Service's Investigative Services Branch. The amount was reached in a pretrial diversion agreement between the men and the U.S. Attorney's Office in the Eastern District of Missouri, and equals the cost of site remediation and the sale price of the erroneously-harvested timber, the release said.

NPS Special Agent Les Seago said Monday morning that the men had been logging on lands outside of the park for about a year, and during their operations they didn't realize they were taking trees from within the park boundaries.

"They were cutting on private property," he said. "They had purchased the rights for timber on this private land that butts up against National Park Service lands, and they encroached into the national park."

While the press release announcing the settlement described a "complex 14-month investigation," Special Agent Seago said most of that time was spent on legal negotiations between the U.S. attorney's office and the lawyers for the two.

An ISB special agent and rangers from the park opened an investigation in March 2013, when a ranger on routine patrol found a logging operation harvesting timber in the area of the Susie Nichols Cabin, inside the park's boundaries, the release said.