The U-S Chemical Safety Board says it has what it calls a "critical new finding" in the October fire at a chemical storage facility in Apex.
The board plans to update the status of its investigation at a news conference scheduled for 11 a-m in Raleigh.
The October fire spewed a yellow-green haze over parts of Apex, prompting town officials to urge as many as 17-thousand people to evacuate. Residents were allowed to return two days later.
Lawmakers in the state House have passed a measure that would require more frequent inspections and closer monitoring of companies that store hazardous waste.
Governor Easley is expected to sign the bill, which incorporates recommendations from a task force that he formed in the wake of the fire.