Holly Poultry, the meat processing and distribution plant where a carbon dioxide incident on Sunday affected 10 employees, returned to normal operations by Monday, the company said in a statement.

Dangerously high levels of carbon dioxide at the Southwest Baltimore-based meat plant led to five employees being hospitalized and five other workers being treated by first responders on Sunday, Baltimore City Fire Department spokesperson John Marsh said.

The source of the incident remains unknown, Marsh said in an email Monday. Fire officials also did not share the current status of those who were hospitalized.

In a statement, Tony Mansolillo, Holly Poultry’s vice president of operations, thanked the fire department for their swift response that led to the incident being quickly contained. In addition to the fire department, Mansolillo said the company is working with the state Department of Occupational Safety and Health and the Department of the Environment.

Mansolillo said Holly Poultry has also hired an industrial hygienist, one who works to prevent workplace health hazards, as one of their steps to “review what occurred and ensure it doesn’t happen again.”

”Holly Poultry is a long-standing part of the Baltimore community, and the safety of our team and neighbors will always be our top concern,” Mansolillo said in a statement.

Dinah Winnick, a spokesperson for MOSH, said they are investigating this incident, but could not provide further details. Representatives for MDE did not immediately respond to a request for comment.

Holly Poultry planted its roots in Baltimore in the early 1960s. Since 1994, it has been family-owned and operated. The meat processing and distribution plant, situated in the Saint Paul neighborhood of Southwest Baltimore, now serves people across the mid-Atlantic, northeast and southeast regions, the company’s website says.

What is carbon dioxide?

Carbon dioxide is a colorless, odorless gas that people regularly breathe. Increased exposure to the chemical, though, has its consequences.

The Centers for Disease Control and Prevention says intaking high levels of carbon dioxide upset one’s respiratory and cardiovascular systems. This could lead to difficulty breathing, dizziness, headaches, increased heart rate and more, the CDC said.