NORTHAMPTON, Pa. -

Hazmat crews are investigating the source of a chemical that made several workers sick at a business in Northampton County on Monday.

The incident happened around 11:15 a.m. in a material recovery facility at Greenstar Allentown, a waste management operation located at 799 Smith Lane in Northampton.

According to officials, 30 people were exposed to an unknown chemical. Five people were taken to the hospital for observation after displaying exposure-related symptoms, officials said. They have since been treated and released.

There has been no word on what chemical the workers came into contact.

"At this point, we have not been able to determine any kind of chemical in the facility," said Robert Mateff, director of the Northampton County Division of Emergency Management Services.

Mateff said it's possible the chemical evaporated or dissolved. Mateff went on to say the public was never in any danger, and said it does not appear there were any environmental impacts. 

Officials believe the incident was contained to the building.

Waste Management officials said the building has since been ruled safe, however, operations will remain halted while officials continue to investigate.

An air quality specialist from the state Department of Environmental Protection has joined the investigation.

A DEP spokeswoman said the smell apparently emanated from a shredder, which released some kind of gas.

Waste Management officials said it appears the chemical came from an item on the sorting line.

"Because they use single stream recycling here, any type of product could have gotten into that and may have been disturbed during the processing part," Mateff said.

In light of that, company officials are urging the public to be cautious and mindful of what they're putting in recycling containers.

"As a facility that accepts materials from commercial facilities as well as residents, we're always asking not to have any types of hazardous household materials in their recyclables.  We just want to point that out," Barthel said.