MINNEAPOLIS (AP) - New data from the Department of Natural Resources show that researchers are beginning to unravel the mystery of what's killing Minnesota's moose.

DNR researchers say preliminary results from following 173 adult moose that were captured and collared from 2013 to 2015 show two-thirds of the 47 that later died succumbed to health problems, while a third were killed by wolves. But of that third killed by wolves, 25 percent had illnesses that made them easy prey.

DNR moose project leader Glenn DelGiudice (DEL'-joo-dees) cautions that the data is just preliminary and it'll take six years of data to draw firm conclusions about long-term trends and causes.

Northeastern Minnesota's moose population has been on a long-term decline, from an estimated 8,840 in 2006 to an estimated 3,450 last winter.