Five people were hospitalized and five more were treated by emergency responders Sunday afternoon after a dangerously high level of carbon dioxide filled a poultry processing plant in Southwest Baltimore, according to the Baltimore City Fire Department.

Dozens of firefighters and emergency responders were on the scene into the evening as officials tried to determine the source of the carbon dioxide.

Fire department spokesperson John Marsh said the five people hospitalized had non-life-threatening injuries.

Workers and truck drivers milled about the scene while fire trucks, ambulances and emergency response vehicles idled nearby.

The incident took place at Holly Poultry, a Baltimore-based firm that has been distributing and processing meat for decades. The company did not immediately respond to a request for comment.