First Nation leaders on Thursday slammed the Canadian National Railway (CN) for neither warning the community of environmental damages caused by the fiery oil train derailment that occurred last Saturday on traditional land, nor even warning of the derailment itself.

Mattagami council member Jennifer Constant said she only became aware of the accident after reading about it on Facebook, despite the community being the nearest in proximity to the crash site.

"We had to initiate contact to get any kind of information, which is a real concern to us considering we were the closest to the incident," Constant told CBC News. She said CN did not get back to her for two days—a charge which CN spokesperson Patrick Waldron denies.

Mattagami Chief Walter Naveau added, "It's [a] big concern from the First Nation because of the environmental impacts of what could happen, the physical damage to the animals and plants. What are the chemicals that are poisonous in there [the crude oil]? We don't know."

The derailment, which occurred late Saturday night, saw 29 train cars carrying Alberta oil sands to Ontario detach from a 100-car freight line, with seven catching fire in an accident which environmental activists say highlights the dangers of fossil fuel transportation. The amount of oil spilled is unknown.

Ontario's Regional Chief Stan Beardy agreed with Naveau. He told CBC on Thursday that First Nation members "still depend on that [territory] for their way of life. They still depend on the animals, the birds and the fish from that area. I'm very concerned that, if there's contamination to the natural environment, that it will affect the quality of the animals, birds and fish."

While cleanup has been ongoing throughout the week and remains underway, CN has reopened its rail lines to other train traffic and says the leak has been contained. Still, Beardy said that neglecting to inform First Nation leaders of the derailment was a major misstep on CN's part.

"It's only fair that the First Nation is notified to the full extent of what is happening, what is being undertaken to address the accident. There should be strong communication between the railway company and the First Nation," Beardy told CBC. "Whoever's responsible has to clean up because the people of Mattagami depend for their livelihood to pursue their traditional activities with that area."

Two tanker cars from the derailment remained on fire as of Wednesday, Waldron said. "Firefighting experts have allowed a controlled fire involving two tanker cars to continue to burn. Those cars are a safe distance from the tracks and present no danger to rail operations or ongoing cleanup work," he said.