An adult at the home, near 9300 South and 3100 West, awoke about 3 a.m. with a headache but went back to sleep, police said. Another adult awoke about 6 a.m. with a severe headache and evacuated the family of seven adults and two children.

Fire investigators detected carbon monoxide levels of 250 parts per million in the basement, where five of the adults slept. Carbon monoxide concentrations above 200 parts per million can cause disorientation, unconsciousness and death, according to the U.S. Consumer Product Safety Commission. Most of the adults declined medical care because of the cost, but the two children and at least one adult were taken to the hospital for observation, police said.

The source of the carbon monoxide was not known Thursday.