MEDFORD, Ore. (AP) — A hazardous materials assessment is underway and cleanup is expected to last a few days after a fire at a gas station Tuesday night in southern Oregon destroyed several businesses and caused a spill of oil.

Medford Emergency Management believes at least four buildings were destroyed in the Medford fire which started at the Carson Pacific Pride commercial fueling station and quickly spread north, The Mail Tribune reported..

The Oregon Department of Environmental Quality and the U.S. Environmental Protection Agency responded to the site, saying in a news release late Wednesday that a sorbent dam had been placed at and near the site. Bear Creek to reduce the amount of petroleum products released into the creek.

The gas station contained large quantities of gasoline, diesel and other petroleum products in aboveground and underground tanks, the Medford Fire Department said.

The EPA implemented community air monitors on Wednesday, state officials said.

“The scene remains dangerous and off-limits to the public,” Oregon DEQ said.

Oiled birds have also been seen and the Oregon Fish and Fire Department and US Fish and Wildlife Service are managing bird response and any other impacts to fish or wildlife.

Medford Police and Medford Fire Department investigators are working to determine how the fire started. The police department said the blaze was first reported as a fire that was heating up near train tracks.