Longview, Washington -- Cowlitz County sheriff's deputies said they arrested a Longview couple after discovering their five adopted children were severely malnourished.

Investigators said Washington State Children Protective Services contacted the sheriff's office in early March.

Detectives said Jeffrey and Rebecca Trebilcock's adopted 13-year-old was taken to Doernbecher Children's Hospital in Portland for broken bones and severe malnourishment. The boy was 4 feet 4 inches tall and weighed just 49 pounds.

Investigators said the couple's four adopted girls, ages 10 to 12 years old, were also underweight and found to be in "neglect" by a pediatrician.

Detectives then took all five children into protective custody.

Investigators said the children told them their parents put an alarm in the kitchen to prevent them from getting food.

The kids reported they were punished if they "stole" food by being put outside and doused with water or hit with a board, investigators said.

Detectives said the 13-year-old boy claimed the beatings were so bad he could feel blood running down his leg.

The children reported they ate dog and goat food, plus dandelion leaves, investigators said.

Detectives revealed the children were seen by a doctor in 2008. Investigators said Dr. Blaine Tolby warned the parents the boy's medical condition was possibly life-threatening and advised them not to postpone a complete medical workup.

Investigators said the adopted girls eat a vegetarian diet and have been kept on the same diet while in protective custody.

As of May 12, the boy has grown an inch and gained 25 pounds, while all four girls have gained 10 to 18 pounds, investigators said.

Detectives said Jeffrey and Rebecca Trebilcock appeared to be well-nourished, plus their three biological children showed no signs of neglect and looked healthy.

Investigators charged the couple with criminal mistreatment and felony assault.

The couple is being held without bail in the Cowlitz County Jail. They're set to appear in Cowlitz County Court Friday afternoon.