Members of the community gather to discuss their safety and other environmental concerns at a town hall meeting following a train derailment that spilled toxic chemicals, in East Palestine, Ohio, U.S.

Hundreds of irate residents of the Ohio town where a train derailed and spilled toxic chemicals packed into a high school gym on Wednesday, seeking answers to what health dangers they face.

East Palestine Mayor Trent Conaway, looking angry and tired, said at Wednesday’s town hall that he wanted to help provide some reassurance for the 4,700 citizens of his town, and hold to account those responsible for the train derailment.

“We need our citizens to feel safe in their own homes,” Conaway said as the meeting began. “I need help. I’m not ready for this. But I’m not leaving, I’m not going anywhere.”

Conaway said Norfolk Southern (NSC.N), which operated the toxins-laden train that derailed on Feb. 3 in East Palestine, was working closely with him. “They screwed up our town, they’re going to fix it,” Conway said.

Conaway addressed citizens seated in bleachers, speaking through a bull horn as he paced around the gym floor.

Norfolk Southern officials did not attend the meeting, saying they feared violence.

“After consulting with community leaders, we have become increasingly concerned about the growing physical threat to our employees and members of the community around this event stemming from the increasing likelihood of the participation of outside parties,” the company said in an emailed statement.

The Norfolk Southern Railroad-operated train’s derailment caused a fire that sent a cloud of smoke over East Palestine. Thousands of residents were forced to evacuate. After railroad crews drained and burned off a toxic chemical from five tanker cars, residents were allowed to return to their homes on Feb. 8.

Much remains unknown of the dangers posed to residents by the toxins that spilled, experts said. Many in the area have complained of headaches and irritated eyes, and noted that chickens, fish and other wildlife have died off. Despite that, state health officials have insisted to residents that East Palestine is a safe place to be.

Erik Olson, the senior strategic director for health and food at the Natural Resources Defense Council, a non-profit group focused on the environment and public health, said the unknown dangers stemming from the derailment vastly outweigh reassurances that officials have given on safety.

“This is clearly a very toxic brew of chemicals,” Olson said. “And I’ve not seen any public accounting for how many pounds or gallons of any of these chemicals that were released.”

The air and water testing that’s been done so far seemed limited and “is not all that reassuring,” Olson said.

He said much more needs to be understood about how the soil and groundwater was polluted from this spill, which he said posed the more significant longer-term danger as opposed to air pollution.

Ohio state officials have said that a plume of pollution in the Ohio River is moving at one mile per hour. But they say cities in the plume’s path can turn off their drinking water intakes as it floats by. They’ve also said that drinking water tests have not raised concerns and normal water treatment would remove any small amounts of contaminants that may exist.

Gerald Poje, a toxicologist and a former founding member of the Chemical Safety Board, an independent federal agency that investigates industrial chemical accidents, said it could take months or years before the scale of the damage is fully known.

“This is a terrible tragedy in Ohio, it’s so painful to see so many lives put at risk,” Poje said. “There is a long challenge ahead of everybody into how to discern risks that are unknown at this moment in time.”

Poje and Olson said an underground plume of pollution could eventually contaminate drinking water and even irrigation wells that farmers may pump up and spread onto crops.

The train of three locomotives and 150 freight cars was headed from Illinois to Pennsylvania when it derailed. The National Transportation Safety Board (NTSB) said 20 of the cars were carrying hazardous materials, including 10 that derailed.

The NTSB said 38 cars in total left the tracks and the ensuing fire damaged an additional 12. The NTSB has not commented on the derailment’s cause.

Railroad union officials have said they have been warning that such an accident could happen because railroad cost-cutting harmed safety measures. But Norfolk Southern said its record has been “trending safer.”