Two convicted killers escaped a Utah prison after guards came up short when doing a headcount Sunday night, officials said.

Danny Martin Gallegos and Juan Carlos Diaz-Arevelo escaped the Daggett County Jail and last were last seen Sunday afternoon.

Helicopter and search dogs were aiding the search, which also includes part of Wyoming.

Gallegos was convicted of aggravated murder in 1991 and Diaz-Arevelo was convicted of murder and child abuse in 2006.

State corrections officials said the two had been transferred to the jail from state prison this summer.