LEWISTON – A gooey black substance used to bond layers of road asphalt has appeared in a small brook behind East Avenue.

The substance apparently leaked Thursday from a parked truck, part of a fleet of vehicles that were at the site near the intersection with Montello Street. That portion of East Avenue is undergoing repaving.

There appears to be no health hazard, assistant fire Chief George Merrill said Thursday night. After all, the chemical is made to be spread on the ground without effects.

However, much is unknown, he said.

Officials knew neither how much of the emulsion, known as “tack coat,” spilled from the truck nor what caused the leak.

“We’re doing research and investigating,” Merrill said.

Pike Industries Inc. of Westbrook has been doing the roadwork, though the emulsion truck was owned by a subcontractor, Northland Paving of New Gloucester, Merrill said.

A worker from the Maine Department of Environmental Protection was called to the scene Thursday evening. Also contacted were representatives of both contractors.

The cleanup could begin almost immediately.

As early as today, Merrill expected to call environmental cleanup company Clean Harbors to pick up the residue from the small brook, which runs behind several homes.

The stuff has made a small mess, Merrill said.

Before it’s spread, the emulsion is kept heated in its liquid form. If it cools, it turns black and sticky, the consistency of crude oil, Merrill said.

In the brook, the chemical cooled and created quarter-sized droplets, he said.