SAN ANTONIO • A pregnant Texas woman has been charged with child abuse after two toddlers chained in her backyard were rescued, following a neighbour's call to police about the non-stop cries of a child in the yard.

When deputies arrived at the house in San Antonio late last Thursday night, they were dumbstruck by the appalling sight of a two-year-old boy bound by a metal chain strapped to his ankle, with the other end fixed to the ground.

They also found a three-year-old girl with a broken arm, tied to the door with a dog leash.

The boy was "chained to the ground as if he was a dog", Bexar County Sheriff's Office spokesman James Keith was quoted as saying by CNN. "There was no slack in the chain. His pants were down. You could tell he'd been here for a while."

Inside the house, police found six more children, aged between 10 months and 13 years. There were no adults around.

"To describe this as disturbing is an understatement," said Mr Keith. "It makes you wonder what somebody's thinking. How could they do this?"

The two children found outside the house were taken to the hospital where the girl was treated for a fractured wrist and arm, and the boy for abrasions and scarring, said the Texas Child Protective Services. The agency added that the children may be malnourished, NBC News reported.

The other six children have been placed in foster care.

Porucha Phillips, 34, mother of the six children inside the house, was arrested when she returned home the next morning with another person.

Phillips, who is pregnant with her seventh child, told investigators she did not restrain the two injured toddlers - who are believed to be siblings - and claimed they had been dumped in her backyard by their parents.

She added that she had been planning to leave them at a fire station as she was unable to take care of them. Her relationship with the two children was unclear, but police suspect she was running an unlicensed daycare operation from her home.

Phillips, who has a record of arrest for soliciting prostitution in Nevada in 2003, now faces two charges of injury to a child by omission with serious bodily injury.

She was being held in jail in lieu of a US$150,000 (S$202,000) bail.

The father of her children has not been charged as he was at work when they were left unattended. He and Phillips are not married.

"They didn't come out much," a neighbour, Mr Chris Tippery, told the San Antonio Express News. "They keep (the children) in the house for the most part.

"Sometimes you would see the kids outside in their diapers."

Another neighbour, who did not want to be identified, said Phillips takes good care of the eight children. "She's a good mother," the neighbour said. "She was just trying to help out."