DALLAS (AP) A 14-year-old boy has confessed to strangling and stabbing his pregnant mother more than 20 times in an attack at the home they shared south of Houston, investigators said Thursday.

Police in La Marque said in a statement that the 33-year-old woman was about five months pregnant when she was found dead in the home Saturday. An autopsy was performed Wednesday and shows most of her stab wounds were to the back and neck.

Investigators have not indicated a motive in the killing but said in the statement that, "The son did provide a voluntary statement in which he confessed to causing the death of his mother."

The teen initially was reported missing but was found a day later in Houston when a family member contacted police.

The boy was charged with a juvenile count of murder earlier this week and is being held at a juvenile detention facility.

The Associated Press is not naming the mother because it would identify the boy.

Investigators have determined that after the killing, the teen took a vehicle that had been loaned to his mother and drove about 200 miles west to Seguin, near San Antonio. He then traveled back to the Houston area before being taken into custody, police said. It's not clear why the boy drove to the San Antonio area.

Authorities have not said when the woman was attacked or how long she may have been dead before a neighbor discovered her body Saturday.

Child welfare officials said the teen and a younger sibling had twice been removed from the woman's custody because of her substance abuse and her partner's domestic violence.

Estella Olguin, spokeswoman for Harris County Child Protective Services, has previously said the teen was first removed from the mother's custody in October 2005 and was in foster care until his paternal grandmother received custody of him in March 2007. He again was removed from his mother's custody in April 2010 and was in foster care until his father was awarded custody in February 2011.