Crews were called to FloChem on Highway 124 near Wellington Road 32 just after 5 a.m.
Firefighters on the scene were told chemicals in a storage area were producing heat and vapours, the Guelph Fire Department said in a news release.
“Two firefighters entered the chemical storage area in encapsulated suits and reported that the spilled products had stopped reacting, resulting in no further production of heat or vapours,” Guelph Fire said.
The spill was contained within the storage area and the Ministry of Environment was notified.
The cause of the spill has not been released and damage estimates are not known.
As a precaution, a stretch of Highway 124 was blocked off by Wellington County OPP for a couple of hours.
Emergency crews cleared the area at around 8 a.m.