Authorities executed a search warrant at the home in Hamden in Vinton County on Tuesday, where they say they found the children and four suspects inside.
Vinton County Prosecutor William Archer said during a press briefing Wednesday that this is not a case of human trafficking, but an "intra-family situation."
The four suspects -- Gary Siders Sr., 73; Christina Siders, 67; Gary Siders II, 36; and Elizabeth Siders, 33 -- have each been charged with 16 counts of endangering children, a second-degree felony, according to officials. They pleaded not guilty during their arraignment Wednesday morning and their bond was set at $300,000 each.
Archer described the suspects as being the "grandma, grandpa, father, and mother."
The charges allege the four suspects abused the children, resulting in "serious physical harm."
Ohio Attorney General Andy Wilson said the evidence in the case is "beyond comprehension."
The children range in age from 1 to 18, according to Wilson. He did not go into the nature of the injuries but said seven of the children were transported to the hospital on Tuesday, including two who were airlifted there. One of the children was in critical condition, Wilson said.
Archer said the children are safe and officials are working to have them placed in temporary custody.
"They are currently in a good situation and are being protected," he said.
Wilson said the investigation has been ongoing for some time, leading to the search warrant being executed on Tuesday.
The family had lived in Vinton County for the past four years and were "clearly bouncing around," according to Wilson.
"They were pretty adept at keeping these kids out of sight and out of investigative eyes," he said.
The children were not enrolled in school, according to Wilson. The eldest child is included among the charges because the 18-year-old is believed to developmentally still be a minor, officials said.
"Some of these children couldn't even speak," Wilson said. "It was terrible."
Vinton County Sheriff Ryan Cain described the condition of the house as "disgusting," including the presence of human feces, and said the children were largely confined to a small area.
"Most of our livestock is kept in better condition than the children," Cain said during Wednesday's briefing.
Ohio Gov. Mike DeWine called the situation "tragic."
"It is heartbreaking to learn the conditions that these children were living in, and to learn of their medical conditions," DeWine said in a statement, which also thanked those helping them.
This is a developing story. Please check back for updates.