MINNEAPOLIS (WCCO) — There were some tense moments at a St. Paul Park recycling company Tuesday when employees complained of sudden throat irritation.

The city’s fire department says emergency crews were called to the Tennis Sanitation company shortly after 1 p.m. on reports of a chemical spill. The employees who experienced breathing difficulties were all treated at the site, which is a recycling processing center for items collected in curbside garbage.

“They’re a recycling and garbage hauler, so where this happened was in the recycling part of the business,” said Fire Chief Kurk Lee. “So they come in and it was something that was inside the recycling trucks.”

Investigators believe someone improperly disposed of a chemical. Once it was inside the building, some worker inhaled the fumes. They are still working on identifying the chemical.