DALLAS —  A teenager was arrested in the death of a 6-year-old foster girl he allegedly threw to the ground at least four times. Now, the state is investigating all foster homes managed by the private agency that placed the girl in the teen's home.

The home was until recently overseen by Mesa Family Services, an agency already under scrutiny for the deaths of two young children in its homes since August 2005.

The girl, Katherine Frances, died Tuesday from injuries she suffered Sunday. The 14-year-old boy, the son of the foster parents caring for Katherine and her three siblings, was being held in a juvenile detention center on suspicion of murder.

Police searched the home Thursday. The boy, who was not named because of his age, is to be charged next week, police Capt. Ron Smith said.

The state also planned on Thursday to begin conducting safety checks on all children in homes formerly managed by Mesa.

"What we have done is launch an unprecedented intervention effort to address the deaths in homes formerly overseen by Mesa," said Patrick Crimmins, spokesman for the Texas Department of Family and Protective Services. "The plan is designed to ensure the safety of more than 300 children in foster homes in more than 20 Texas counties."

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"If they find any unacceptable risk in any of the homes, they are going to remove children immediately," he said.

The state stopped placing children in Mesa's homes earlier this year after the September death of a 16-month-old girl and the August 2005 death of a 3-year-old girl. Both died of head injuries.

Mesa voluntarily dropped its foster-care contract with the state, and last month, the state moved to revoke Mesa's child-placing agency license.

Therapeutic Family Life took over at least 90 of Mesa's foster homes, including the home where Katherine died. On Tuesday, Protective Services ordered Therapeutic to temporarily stop placing new children in homes while officials investigate, said agency spokeswoman Marissa Gonzales.

Eli Bell, attorney for Therapeutic Family Life, said the company doesn't have much information on what transpired at Katherine's foster home.

"We were working very closely with ... (state child welfare services) and monitoring that home and the children very closely, and it looked like the children were properly placed and in a safe environment," he said.

A woman reached by phone at Mesa referred calls to Therapeutic.

Katherine and her three siblings had been temporarily removed from the foster home only days before her death. The foster mother had taken Katherine and her 8-year-old sister to a hospital with bruises on Nov. 25. The foster parents told police the girls injured themselves fighting.

Bell said the four siblings, ranging from age 5 to 11, were put in temporary foster care while Therapeutic and the state investigated and were later returned to the home after investigators determined the living conditions were safe.

The children had been removed from their mother's custody in July because state investigators said the mother would leave the children alone, didn't provide food for them and had no electricity.

Katherine's siblings are now in their grandparents' custody.

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