OSHA is investigating the carbon monoxide leak that sent 19 employees at Fargo's Red River Commodities to the hospital.
OSHA Area Director Eric Brooks says the agency will examine all equipment inside the bird food company to make sure it was properly inspected in the past and is working correctly.
The statute of limitations gives OSHA six months to complete the investigation.
Firefighters say overhead gas powered heaters were the likely the cause of the problem on Wednesday afternoon. It was the second major carbon monoxide scare in the metro in a week.
Dozens were sickened Sunday during hockey games at Teamsters Arena in north Fargo.