Authorities spent much of Saturday afternoon searching for the cause of a small oil spill found in the Penobscot River, which ran from Brewer to Orrington.

Capt. Brian Houston of the Brewer Fire Department said at the scene that Brewer firefighters received a call from the Department of Environmental Protection after a resident reported seeing the oil in the water. The DEP also called the Bangor Fire Department, which could find no trace of the oil in the water in its side of the river. Also, said Houston, a pilot flying from Bangor International Airport reported seeing the spill while flying over the Veterans Remembrance bridge. The oil was then on the Bangor side, Houston said, and could have been shifted to Brewer by the river current.

By Sunday morning, the oil had dissipated, and the cause was never discovered, Houston said Sunday afternoon. Houston said that a DEP official said the oil could have been the remnants of an earlier spill, released because of the ice thawing.

The oil slick, which ran out about 25 feet from the shore of the river in Brewer, was discovered later near the Snow’s Corner extension in Orrington, about three-quarters of a mile from the apparent origin, Houston said.

The oil type also was never discovered. While a representative of an oil company told Houston that the oil appeared thicker than fuel oil, Houston said that the Brewer Treatment Plant was running tests on the liquid.