Northampton County dispatchers said medics transported five employees from a recycling plant after they were exposed to some sort of chemical.
The hazmat situation occurred around noon Monday at the Greenstar Allentown recycling plant on Smith Lane in Northampton, Pennsylvania.
The plant, which separates recyclables from businesses and residents, is operated by Waste Management.
Company spokeswoman Patty Barthel said that employees were separating materials as they normally do Monday when one of the items emitted an odor that caused some of the workers to become sickened.
Barthel said that they immediately stopped the line and evacuated all 29 employees.
Crews rushed to the scene and dispatchers referred to the incident as a "mass casualty" situation because of how many people were inside at the time.
Barthel said however that all employees were able to leave the building on their own power and were checked out at the scene by medics.
Five of the workers were treated and released from an area hospital, according to Barthel.
As SkyForce10 hovered overhead following the incident, crews and firefighters could be seen working outside the warehouse.
Crews couldn't immediately determine what chemical caused the incident. Barthel urged everyone who recycles to not recycle anything hazardous.
The company sent all workers home for the day and hoped to resume recycling Tuesday, according to Barthel.