The children, ages 3 to 12, were dropped off at a South Oak Cliff fire station in Dallas Sunday morning, The Dallas Morning News reported.
Dallas Fire Rescue spokesman Jason Evans said two women stopped by a friend's house to check on her children earlier Sunday and discovered the kids were unsupervised. The women then brought the children to the fire station.
The children could not say how long they had been alone.
Child Protective Service agents were called in and have since talked to the children's mother, KXAS-TV, Dallas/Fort Worth, reported.
"CPS workers were able to identify and meet with the mother of the children and are still investigating the circumstances under which they were left alone. The children were placed in foster care and will remain there temporarily while the investigation continues," DFPS spokeswoman Marissa Gonzales said.
The children have been placed in foster care and in good health, Gonzales said.