El Cajon, CA — Five people were taken to the hospital Tuesday afternoon after reportedly falling ill at an El Cajon animal hospital.

The incident was reported at around 1:40 p.m. at the Care & Comfort Veterinary Hospital on 522 E Chase Ave.

According to Heartland Fire officials, five adults and two children inside the hospital reported not feeling well.

Responding emergency crews conducted tests on the adults and children, and they found the seven people had elevated levels of carbon monoxide in their systems.

The adults were transported, but the two children — for reasons unknown — were not taken to the hospital.

Fire officials said a hazardous materials team and county health officials tested the air in the building but could not locate the source of the carbon monoxide.