FORT WORTH -- The parents of a toddler who slipped through a pet door and was mauled by dogs in the back yard of his grandparents' home were arrested Thursday and face charges of injury to a child, authorities said.

Chance Walker Sr., 25, and Patricia Walker, 23, knew that the dogs were aggressive and had injured people and that their son, Chance Walker Jr., could get out of his playpen and into the yard, according to an arrest warrant affidavit released Thursday.

The Walkers went to sleep during the day without taking measures to protect their son from the dogs, the affidavit says.

They were in the Tarrant County Jail on Thursday with bail set at $100,000 each. The maximum sentence on the charge is 20 years in prison and a $10,000 fine.

Doctors at Cook Children's Medical Center reattached one of Chance's ears, and he has been released from the hospital, a spokeswoman for Child Protective Services said. But he will need more treatment.

CPS took custody of the boy soon after the attack, and he was in foster care Thursday, spokeswoman Marissa Gonzales said.

A hearing in his custody case is set for 8:30 a.m. today in Fort Worth.

"CPS will testify about the case, the evidence that led to the removal and how the child is doing," Gonzales said. "The judge will then decide what, if anything, the parents can do to try and get their child back."

The dogs were euthanized.

The couple were arrested about 11:30 a.m. Thursday at a home in the 900 block of Hackamore Street in White Settlement, authorities reported.

They had been staying with Chance Walker Sr.'s parents in the 7800 block of Eastland Drive in unincorporated northwest Tarrant County.

According to the sheriff's affidavit and a CPS affidavit, the couple were known to sleep through the day and had a history of drug abuse.

On Jan. 31, Patricia Walker tested positive for methamphetamine hours after her son was mauled, and her husband refused to take a drug test, the affidavits say.

Deputies questioned the couple at the hospital Feb. 1 and asked them to go to the Sheriff's Department on Feb. 3 to give a statement about the attack.

They did not show up.

Deputies had responded to complaints about the dogs six times.

The Walkers were investigated by CPS caseworkers beginning in September 2010 and tested positive for methamphetamine, investigators reported.

The couple completed outpatient drug treatment, and the case was closed.

During those investigations, the couple took four drug tests, testing positive for methamphetamine twice and negative twice, according to a CPS affidavit.

Chance Walker Sr. told CPS officials that he had smoked methamphetamine since he was 12, and his wife told authorities that she started using it in August 2010, CPS' affidavit says.

Staff writer Mitch Mitchell contributed to this report.

Domingo Ramirez Jr.,

817-390-7763

Twitter: @stcrime