HUNTING — A bighorn sheep die-off caused by disease has triggered the closure of hunting for the animals just outside Yellowstone National Park.

Montana Wildlife officials said Monday that at least 34 bighorn sheep have died in the pneumonia outbreak that began late last year near Gardiner, Montana. That’s almost 40 percent of the herd that ranges in the Gardiner and Cinnabar areas north of Yellowstone.

Wildlife commissioners issued the closure during a Monday conference call and said it would reopen when the population recovers.

Sheep in the Gardiner area have experienced smaller pneumonia outbreaks in the past few years.

There are domestic sheep in the same area. State officials say bacteria can be transmitted from healthy domestic sheep to bighorn sheep, causing pneumonia in the wild animals.