PRINCETON, Minn. (AP) - A federal agency has closed its investigation into a plane crash in east-central Minnesota that killed a man on his way to a hunting trip.

Fifty-one-year-old Kevin Covlin (KAHV'-lin) of Princeton died when his plane crashed on takeoff from the Princeton airport in October 2013. No one saw the crash.

Reports say the National Transportation Safety Board says Covlin lost control of the plane but the cause remains undetermined.

Toxicology tests showed Covlin was exposed to carbon monoxide, but ruled that out as a cause of the crash, saying the amount would have only given him a headache.

The NTSB reported that since fire destroyed the plane and contents, it was unable to determine whether luggage and equipment had been improperly loaded, creating an unstable airplane.