POCATELLO — Authorities have cleaned up much of a massive mineral oil spill that made its way from a north side industrial park to Pocatello Creek and the Portneuf River.

City officials said Monday that Virginia Transformer Corp. confirmed that 6,000 gallons of mineral oil, a highly refined petroleum substance, was released last week from a rail car at its facility at the Titan Center, also known as the former Naval Ordnance Plant.

The oil traveled into a storm drain connected to Pocatello Creek, which connects to the Portneuf River in north Pocatello.

People walking along the Pacific Recycling Trail on Wednesday afternoon noticed the oil spill in Pocatello Creek near where it meets the Portneuf River and immediately reported the spill to the city.

The Pocatello Fire Department and Idaho Department of Environmental Quality responded and worked quickly to place booms in Pocatello Creek in an effort to prevent the spill from spreading into the Portneuf River.

Cleanup crews from the Environmental Protection Agency, DEQ and Pocatello Public Works Department worked continuously on Thursday and Friday to keep the spill contained.

City officials said there was “a light intermittent sheen” from the oil that could be seen on the Portneuf River on Friday but it didn’t seem to be affecting fish or other wildlife. No public health concerns were identified by the EPA personnel at the scene, according to the city.

On Monday the city reported that 1,800 gallons of the oil had been collected thus far and cleanup crews have prevented most of the oil from reaching the Portneuf River.

City officials said an investigation is being conducted to determine why the oil was released from the rail car at the Virginia Transformer facility.

The EPA is conducting and funding the cleanup which will continue over the next several days, the city reported.

Pacific Recycling Trail has been closed until further notice because of the spill.

Anyone with questions or concerns about the spill should contact City Public Works Director Jeff Mansfield at 208-234-6212 or Bill Dunbar with the EPA at 206-245-7452.