CAÑON CITY, Colo. (CBS4) – The death toll for former wild horses at a federal holding facility in Cañon City has risen to 136. The Bureau of Land Management said an equine flu virus outbreak is likely to blame.

Horses do not face these kinds of outbreaks in the wild.

The Wet Mountains overlook the pens of the East Cañon City Prison Complex. (credit: Mark Neitro, CBS4)

Advocates said this mass-casualty event is emblematic of how the BLM continues to fail federally-protected wild horses.

(credit: CBS)

Last week, the BLM released this statement to CBS4:

“We are working with local, state and federal officials to determine what is impacting horses in the facility and how we can respond as effectively as possible.”

Some 2,500 horses were in a government holding facility in Canon City. The BLM says the horses were gathered from the West Douglas round up near the Colorado-Utah border in the fall of last year and there are plans to round up thousands more.