City health inspectors found unnaturally high levels of three types of metals in the soil near a Coconut Grove park and elementary school.
"You never know the blind dangers," said resident Arrafi Horne.
Inspectors tested the soil at the Miami Fire Rescue Training Center at 3425 Jefferson Street ahead of a proposed expansion.
"Those test results came back with three positive findings, I think for arsenic, cadmium, and I forget the name of the third metal," said Commissioner Marc Sarnoff. "The arsenic is a natural occurring metal in South Florida and the other two could be contributed to ash or some contamination."
Fifty years ago, the training center was home to an incinerator nicknamed Old Smokey. It burned waste and turned it into ash.
Could that be the cause? No one knows.
"All we know is that in the ground there were some positive findings," said Sarnoff.
Old Smokey is now where the fire fighters train. Feet away is Armbrister Park, and then feet away from that is Carver Elementary School.
James Nevins' daughter goes to the school. He's especially worried because he faced a similar issue in New Jersey.
"Actually, where I'm from is probably the highest case of cancer in the country," he said.
Commissioner Marc Sarnoff said the health of the community paramount.
"Nobody wants to send their kids out to play in contaminated soil."
He also said it's important to wait and see what the facts are before panic sets in.
The first round of results for the park could come in as early as Friday.