This is an archived article that was published on sltrib.com in 2015, and information in the article may be outdated. It is provided only for personal research purposes and may not be reprinted.

It will take time before health experts know what type of substance spilled into Mill Creek on Friday, and how it got there.

A passerby walking through Fitts Community Park, near 3050 S. 500 East, first noticed an oily sheen on the surface of the creek at about 7:30 a.m. Friday. Hazmat crews, firefighters and police rushed to the scene and contained the substance, which as of Friday afternoon, remained a mystery to the Salt Lake County Health Department.

"It's still under investigation. We have not yet identified a source, or identified the material itself," said John Hoggen, the department's emergency response coordinator. They've sent samples to a state lab on a rush order, but it could take until Tuesday before all of the results come back, he said.

The oil appeared to have entered from a storm drain somewhere above 700 East and was reported to have spread as far away as 200 East. The storm drain is fed by three canal and drainage inlets.

Unified Fire Battalion Chief Brian Anderton said the leak did not appear to be large and was not thought sufficient for public health concern — though experts were on site to gauge any environmental or wildlife impact.

"Hazmat has some booms in the water, trying to contain it, and we're testing [the oil] to better know where it may have come from," Anderton said early Friday.

The booms will remain in place until the health department can figure out what the substance is, Hoggen said.

By Friday afternoon, hazmat crews reported they had contained the oil's spread to roughly a five-block span of the creek.

Salt Lake County Health Department officials said they had no reports of human or animal or wildlife injuries or ailments related to the spill.

Twitter: @remims, @mikeypanda