The Haz-Mat unit of the Springfield Fire-Rescue Division worked Thursday afternoon under the Buck Creek bridge on North Limestone Street, hoping to stop some kind of leak in the water.

"We're trying to get ahead of it right now," Battalion Chief Kevin Sprinkle said.

A blue-green discoloration in the water initially was reported before noon Thursday on Springfield's east side, Sprinkle said.

What it is and where it came from remains a mystery, he said. The division placed a boom in the water downstream to absorb it, but the substance appeared to dissipate before reaching that point.

The division sampled the water, Sprinkle said, but the tests didn't show any substances. It also notified the Ohio Environmental Protection Agency.