Dan Harshburger, a spokesman for Martin County Fire Rescue, said the building in Jensen Beach was evacuated at 10:41 a.m. Thursday as investigators worked to identify an "unknown substance leaking from two cardboard boxes," TCPalm.com reported Friday.
"They did air monitoring inside the building, they found nothing," Harshburger said. "They've done an evaluation of the substance, and at this time they determined they believe it to be possibly moonshine."
Martin County Sheriff's Office spokeswoman Rhonda Irons said officials examined the contents of the boxes and found one of them contained a broken jar labeled "moonshine."
Harshburger said two people were taken to a hospital for evaluation during the incident.
The spokesman said he did not know whether the moonshine was legal.