An elementary school in Oklahoma City was temporarily closed Tuesday, a day after three students and three teachers were sickened by carbon monoxide. The six children and adults from Lee Elementary School who were taken to hospitals Monday afternoon were reported to be in good condition after examination, The Oklahoman reported. Four other people were treated at the school. Tierney Tinnin, a spokeswoman for Oklahoma City Public Schools, said the carbon monoxide appeared to have been leaking from a new heater. She said the school was closed while the heating unit is replaced. Oklahoma Natural Gas and the Oklahoma City Fire Department were summoned to the school after several people complained of nausea and dizziness.