(NewsNation) — Did the Environmental Protection Agency (EPA) and Norfolk Southern keep concerning test results for toxic chemicals in East Palestine, Ohio, secret from the public?

That’s the question in response to a damning whistleblower report exclusively obtained by NewsNation on the eve of the one-year anniversary of the train derailment.

The non-profit group, Government Accountability Project (GAP), claims the EPA tested nearby soil and water much earlier than previously disclosed to the public.

The group says the EPA found an elevated level of dioxins during those tests — but continued to tell residents they were safe from the chemicals spilled and burned after the train derailed.

Nearly a month after officials burned 116,000 gallons of vinyl chloride over East Palestine, the EPA — under public pressure — ordered Norfolk Southern to test for dioxin, a toxic, carcinogenic compound created when burning chemicals like vinyl chloride.

That decision put the EPA in the hot seat in front of congress.

“Why did you wait a month before you started to order the dioxin testing, when the community was asking for this?” asked Sen. Shelley Capito, R-WV.

“Senator Capito, our air monitoring was searching for primary indicators such as phosgene and hydrogen chloride. Immediately during and after the burn, we detected very low levels which very quickly, and even down to non detect,” said Debra Shore, the EPA’s regional administrator.

NewsNation has been committed to covering the fallout of the East Palestine train derailment over the last year. Here are the most recent updates:

• East Palestine health issues persist one year after Ohio train derailment
• East Palestine creeks visibly contaminated year after train derailment
• President Biden to visit site of East Palestine toxic train wreck
• Cleanup costs exceed $1 billion Norfolk Southern announced layoffs
• Ohio train derailment: Have cleanup demands been met year later?
• East Palestine considering accepting wastewater
• Norfolk Southern joins safety hotline that protects workers

“You know, they had done testing. And we found that out that they’ve done testing on waste products and found very high levels of dioxin and in these waste products, so I mean, they already knew there was an issue with dioxin,” said Lesley Pacey, an investigator with the GAP.

The GAP found documents that show the EPA, Norfolk Southern and its paid consultant Arcadis conducted dioxin and related testing on Feb. 9 and Feb. 17, 2023. They found elevated levels of dioxin and other dangerous compounds in East Palestine despite saying otherwise, publicly.

“They didn’t want people to know they had dioxin concerns here. Dioxin is the most toxic substance known to man,” Pacey said.

So what did the Feb. 17 results show? “It shows a TEQ dioxin level of 91.9, which is 19 times higher than the 4.8 screening level, which requires more testing,” said independent testing expert Scott Smith.

NewsNation asked the EPA and they said, “EPA and Norfolk Southern began off-site dioxin and furan sampling in March… On-site dioxin and furan sampling of waste began in mid-February.”

“It’s word gymnastics. I mean, I’m sorry. This off site on site, you know. It doesn’t make any logical sense. It’s basically the EPA trying to mask something,” Smith said about the EPA’s response.

“They didn’t want to talk about that. They didn’t want that information out. But I’ve been speaking with scientists some off the record, some on the record, and they’re all very concerned. And clearly the EPA scientists that handled dioxin were concerned from the get go, that this was a tremendous dioxin event, potentially. Why the delay on testing? Why the all the excuses?” Pacey said.

NewsNation asked the EPA for an interview but they declined.