FLINT, Mich. (AP) — Authorities focused on a chemical company Thursday as the likely source of a spill that has left a dark oily sheen for miles on the Flint River.

Lockhart Chemical in Flint was cooperating with state regulators and removing material from underground storage areas, said Jill Greenberg, spokeswoman at the Department of Environment, Great Lakes and Energy.

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The spill, which started Wednesday, was coming from a storm sewer that discharges into the Flint River, she said.

“The leak is ongoing. We’re still in emergency response mode,” Greenberg said. “Right now, our focus is on stopping the leak and protecting the Flint River.”

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Samples will be sent to labs for analysis. Messages seeking comment were left for Lockhart Chemical, which makes coatings, metalworking additives, hydraulic fluids and lubricants.

The Genesee County health department told people to avoid contact with the river.

Officials said Flint’s drinking water was not threatened. Flint used the river for drinking water in 2014-15 before lead contamination caused the city to return to Lake Huron water provided by a regional supplier.

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