HOUSTON -- A 9-year-old girl and her 10-year-old brother were stabbed multiple times by a relative with a history of mental problems, officials told KPRC Local 2 Thursday.

"The girl got stabbed in the head and then neck and some in the back," neighbor Gary Epps said. "The boy … he got stabbed like 13 times."

Harris County sheriff's deputies said Regina Umagat, 28, started banging on the door of a home in the 8200 block of Greens Road at about 8 p.m. Wednesday. Investigators said she was screaming that she had "stabbed the children."

The children had been adopted by their grandparents. They were being cared for by their aunt, Umagat, while the grandparents went to a store, officials said.

When deputies arrived at the scene, they found Umagat laying on the driveway with her hands interlocked behind her head. Detectives said she told them that she had stabbed the children and they were at a home across the street.

Deputies went to the home, but the children were not there. A few minutes later, a call was made to the sheriff's office to advise them that two juvenile stabbing victims were at Northeast Memorial Hospital's emergency room.

Investigators said the children's grandparents had arrived home and taken the children to the hospital before deputies arrived.

The children were later flown to Memorial Hermann Hospital in critical but stable condition. They were expected to survive.

Investigators said the boy was stabbed multiple times on the top of his head, left forearm, upper chest, the right side of the back and right shoulder. The girl was stabbed once in the cheek and once close to the center of her chest, detectives said.

Neighbors said Umagat has mental health problems.

"Kind of bipolar … real quiet and always stayed to herself," Epps said.

Umagat has been charged with two first-degree felony counts of injury to a child. She is being held in the Harris County Jail without bond.

Investigators do not know what triggered the attack.

Child Protective Services said Umagat has no prior history of abuse.