(CNN)Investigators probing the toxic train disaster in East Palestine, Ohio, are reviewing multiple videos of the train prior to it derailing.
One video shows "what appears to be a wheel bearing in the final stage of overheat failure moments before the derailment," the National Transportation Safety Board said in a statement Tuesday.
"The suspected overheated wheel bearing has been collected and will be examined by engineers from the NTSB Materials Laboratory in Washington, D.C," the statement said.
The wheelset will undergo a metallurgical examination as part of the overall investigation. Investigators will return to complete an examination of the tank cars once they are fully decontaminated, the NTSB said.
Investigators have not yet determined what they believe caused the disaster. Such a determination typically takes many months.
The NTSB said it is reviewing other videos, too, including footage from two local businesses reported by local media to show glowing or flames from the train prior to the derailment.
The agency is also reviewing recording data from the train's so-called black boxes, including an event recorder and image recorders.
The train carrying hazardous materials, including the toxic chemical vinyl chloride, derailed February 3, prompting evacuation orders for residents in the village of 5,000 people near the Pennsylvania border.
The wreckage burned for days as authorities worried about the possibility of a widespread, deadly explosion. But crews managed controlled detonations to release the chemical, which can kill quickly at high levels and increase cancer risk. The hazardous substance spilled into a trench, where it was burned away.
The state's public utilities commission told Ohio Gov. Mike DeWine that the train was not considered a "high hazardous material train," DeWine told reporters Tuesday, an assertion he said he found "absurd."
If that's correct, he said, "Congress needs to take a look at how these things are handled. We should know when we have trains carrying hazardous material that are going through the state of Ohio," DeWine said.
In an update Tuesday, investigators said no vinyl chloride has been detected in any of the down-gradient waterways near the train derailment, and environmental teams are aerating waterways near the site.
While there are some waterways that remain contaminated, the Ohio Environmental Protection Agency is confident that the contaminants are contained, said Tiffani Kavalec, chief of the division of surface water at the agency.
What Kavalec described as "fire combustion chemicals" did flow to the Ohio River, "but the Ohio River is very large, and it's a water body that's able to dilute the pollutants pretty quickly," she said.
The chemicals are a "contaminant plume" that the Ohio EPA and other agencies have been tracking in real time. It's believed to be moving about a mile an hour, Kavalec said.
The "tracking allows for potential closing of drinking water intakes to allow the majority of the chemicals to pass. This strategy, along with drinking water treatment...are both effective at addressing these contaminants and helps ensure the safety of the drinking water supplies," Kavalec said, adding that they're pretty confident that the "low levels" of contaminants that remain are not getting passed onto customers.
Still, authorities are strongly recommending that people in the area use bottled water for drinking, especially if their water is from a private source, such as a well.
About 3,500 fish across 12 different species have died in Ohio's waterways following the spill, Mary Mertz, the director of Ohio's Department of Natural Resources, said.
None of the 12 species affected are endangered or threatened, but it's "still a loss of life, all the same," she said.
The estimation of the dead fish came after initial testing and sampling by the state agency, Mertz said. There does not appear to have been an increase in the number of fish killed since the first couple of days following the derailment.
There has been no evidence of non-aquatic species suffering from the derailment, she said, and they haven't had any concerns about that.
Almost 500 cubic yards of "vinyl chloride-impacted material" has been removed, according to the Ohio EPA, and cleanup of contaminated dirt near the derailment site continues.
Some of the pits of dirt that have been dug up measure about 700 feet long and 8 feet deep, Kurt Kollar, the on-scene coordinator for the Ohio EPA's Office of Emergency Response, said.
Almost a million gallons of water have been collected and stored in containers on site, Kollar said.
By next week, most "high-end, daily" emergency environmental responses should be in their final stages, he said.
When asked about anecdotal reports of people getting headaches and sore throats, and of animals, such as cats and chickens, dying near the train derailment, Ohio Health Director Dr. Bruce Vanderhoff said that air quality does not appear to be the source.
"Anecdotes are challenging because they're anecdotes," Vanderhoff said. "Everything that we've gathered thus far is really pointing toward very low measurements, if at all."
People with those symptoms should contact their medical provider and call the local hotline so a team can check that environment, he said.
Correction: An earlier version of this story misspelled the first name of Ohio Environmental Protection Agency official Tiffani Kavalec.