Nine sick and malnourished horses were seized from a Morton farm last week due to poor conditions.
One horse had to be euthanized, the Lewis County Sheriff's Office reported Monday.
The horses' owners, Terry and Joanne Simmons, may face first degree animal cruelty charges as a result.
Deputies were initially tipped about possible animal neglect at the Simmons' property, located on the 800 block of State Route 7 in Morton.
The Simmons were ordered to provide the horses with veterinary care, but failed to do so, deputies said.
Deputies said the Simmons agreed the horses needed care and were cooperative.
The horses were removed on Friday and will begin receiving care with help from such as animal rescue groups as Dwelly Farm, Hope for Horses, Pasados Safe Haven, Good Life Stables, Hooved Animal Rescue of Thurston County and the Lewis County Animal Shelter.
Grain and feed donations can be made to the Lewis County Animal Shelter.
The Lewis County Prosecutor's Office will decide on any possible criminal charges.