BRISTOW, Oklahoma - A potentially toxic site is causing concern in Bristow, and now the federal government is getting involved.

The Environmental Protection Agency is trying to determine if an abandon oil refinery poses health risks to an entire community.

The Wilcox Superfund Site is an abandoned oil refinery that's so potentially toxic the federal government put up a fence to keep people out.

Three years ago, Pastor Mark Evans and his congregation had to abandon their church because of potentially toxic sludge.

"People had been born in that church, married, had funerals in that church, so a lot of memories. Lives were changed in that church so a lot of memories attached to that building," Evans said.

He had to up and move his church and his family - who lived next door - after his son found black sludge in a nearby creek.

Evans said, "We went down there and I saw an oily sheen on the surface of the water. And I said, ‘Christian, there's something wrong with that creek. I don't want you playing down here.’"

That kick-started the Superfund process, by which the EPA is working with the State Department of Environmental Quality to find out what is contaminated, and how much.

"What's wrong with the site? What contaminants are there? Where are they located," said Katrina Higgins-Coltrain with the EPA.

The EPA said it tested all the groundwater wells in the area and they're all safe to drink, but it did find air contamination in some vacant buildings and it's still testing ground soil samples.

Neighbors are worried about the consequences for their health and want answers, but the EPA said the process is a long one.

"I'm hoping that by 2019, 2020, we can start looking at technologies and make a decision, and we can move forward with clean-up by 2021," Higgins-Coltrain said.

If you'd like to follow along the timeline of what the federal and state governments are doing for the Wilcox Superfund site, you can do so here.