HOULTON – The Department of Environmental Protection was continuing efforts Thursday to find the source of oil seeping into Pierce Brook near Sugarloaf Street.

Carl Allen, an oil and hazardous materials specialist from the DEP’s Presque Isle office, was at the site Thursday putting down absorbent pads and setting up containment booms.

For the past few years, there have been scattered reports of a sheen on the water in the brook. The DEP has checked each report and found that it was organic in nature.

An organic sheen, Allen explained, is caused by the breakdown of organic material often found in swampy or boggy areas. When touched, it breaks up easily.

An oil-based sheen does not break up and there could be an oil smell present.

Allen said the latest sheen was reported Tuesday, and this time there was an oil odor.

Heavy equipment was brought into the site and a test pit was dug in the spot believed to be where the oil was seeping from. There was no clear source of the oil, however.

“At this point in time, it could be from anything,” Allen said. “We may never know.”

He said it could have come from the old L.E. MacNair Co. building where the Environmental Protection Agency in the early 1990s spent more than $1 million to clean up hazardous chemicals. The building was partially torn down in 1996, and fire destroyed the remainder later that same year.

The source also could have been from the Bangor and Aroostook Railroad, which has tracks that pass the site, or from an old service station anywhere in the area, he said.