Authorities were called to a home in San Antonio early on Friday morning after a neighbour reported hearing a child crying for a long time.
A three-year-old girl was also found tied to an outside door by a dog lead.
Police found six more children alone inside the home, ranging in age from 10 months to 13 years old.
Police arrested the parents of six of the children when they arrived home later on Friday.
"It's sickening," Bexar County Sheriff's Office spokesman James Keith told the San Antonio Express News.
"To call this horrific would be an understatement. If it wasn't for our deputies and this caller who tipped us off, we know that this could have had an even worse outcome."
The three-year-old girl had a broken arm and was treated at a local hospital. A state agency is now caring for the children.
Police are searching for the parents of the other two victims.
Police in the US state in Texas have rescued eight children from "horrific abuse" including a two-year-old who was chained to the ground in a garden.