(AP) -- Activists in Nevada are questioning the rising death toll from a government roundup of wild horses from the range north of Reno.

U.S. Bureau of Land Management spokeswoman JoLynn Worley says 77 mustangs involved in the Calico Mountains Complex gather have died so far - 70 at a Fallon facility where they were taken and the rest at the roundup site.

That's nearly double the 39 horses that had died when the roundup of 1,922 concluded on Feb. 5.

Horse advocates are pressing the government for measures to deal with the situation.

Worley attributes the deaths mostly to the poor body condition of mares that were sent to Fallon, where the are being prepared for adoption or transfer to pastures in the Midwest.