"I want the public to know that they don't have to handle this case alone (...). We will be there to help," said the head of the US Environmental Protection Agency (EPA) , Michael Regan, who went there, in East Palestine, in the northeast of the country.
Mr Regan said no traces of vinyl chloride or hydrogen chloride were detected after more than 480 homes were examined, and the water was tested and re-tested "to ensure that these communities are protected".
“We are going to shed light” on what happened, assured for his part in Washington the spokesperson for President Joe Biden, Karine Jean-Pierre.
And "we are going to hold Norfolk Southern to account", the railway company operating the train, she added.
On February 3, the derailment caused a huge fire and the evacuation of several hundred people.
Among other things, the train was carrying vinyl chloride, a carcinogenic and highly flammable chemical used in the manufacture of plastic.
The railway authorities then proceeded to "controlled" releases of vinyl chloride "to avoid a possible explosion" according to the office of the governor of Ohio, releasing toxic fumes into the air.
Since then, the case has continued to gain momentum, as residents have expressed their concern.
Some have reported to the media that they had had various symptoms, including headaches, and said they feared they would end up with cancer in a few years.
Some 3,500 fish also died in surrounding waterways, according to the local natural resources agency.
Based on tests, authorities said the air was "safe" and that municipal system water tests had detected no pollutants.
However, they advise people using water from private wells to have it tested and to continue drinking bottled water while awaiting the results.
The inhabitants, who have been authorized to return to their homes, display their mistrust.
One told the local channel WKYC that the residents were "suspicious, paranoid and worried".
Another shared her "fear".
"I fear for my family, I fear for my city," Kelly Felger told CNN.
© 2023 AFP