Lakewood Elementary School in Dallas will be closed again Wednesday because carbon monoxide was again detected in the school's boiler room.
Dallas ISD announced classes were canceled for a second day just a short time after telling parents the school would be open.
Officials explained no carbon monoxide was detected in the classrooms early Wednesday morning. But then the boiler was turned on and the levels started rising again.
Parents are reportedly being turned away in an abundance of caution for the students, DISD said.
Workers hope to fix the problem before Thursday.
On Tuesday, students were evacuated and taken to Lakehill Prep.
Officials said more than 60 students and four staff members reported not feeling well at the end of the day Monday.
A contractor inside the school picked up high readings of the gas. A subsequent investigation found a dead owl in the ventilation system that caused improper venting of a furnace in the school's basement.
There are no carbon monoxide detectors at the school because they are not required by law.