EAST PALESTINE, Ohio — Nearly five months after a train derailment and fire unleashed a massive plume of toxic chemicals on this town of 4,700 people, federal investigators Wednesday reassured exasperated residents that they are thoroughly reviewing the incident and will make recommendations — and fight to get them implemented to prevent another disaster.

Dozens of residents packed a high school auditorium on the eve of an investigative hearing that has summoned railroad officials and federal regulators to East Palestine for two days of questioning and discussion about the Feb. 3 derailment. Some residents said too many questions remain about the incident, the chemicals that spilled and the continuing effects on their community, while others urged more accountability of the rail industry and federal regulators.

"It's frustrating," Laurie Harmon, a resident who lives near the tracks, told National Transportation Safety Board Chairwoman Jennifer Homendy at the meeting.

The meeting hosted by the NTSB preceded a rare, two-day hearing in East Palestine as part of the agency's ongoing investigation into what led the Norfolk Southern train to derail and the subsequent hazardous material release and fires. Since the incident, which drew national headlines for weeks, the U.S. Transportation Department has issued more safety measures and advisories, and called on Congress to update railroad laws. Ohio's two U.S. senators introduced bipartisan legislation to increase safety standards for railroads.

The NTSB is expected to question witnesses, focusing on four areas of inquiry: the emergency response to the incident; the steps that led to the vent and burn of five vinyl chloride tank cars; the railroad's use of track defect detectors; and the integrity of the tank cars and rail equipment.

"We are so sorry that this tragedy occurred. We are sorry for everything that you are going through," Homendy told the residents.

While the NTSB could make recommendations during and at the completion of the investigation, some residents said they are concerned the recommendations will be implemented only voluntarily.

"There is a lot of focus in Congress now about improving rail safety, and I am hopeful that they will take our recommendations seriously and implement those," Homendy said. "We'll continue to fight for them. This isn't just a paperwork exercise. ... We fight really hard."

Although the odor of chlorine that filled the air in the aftermath of the derailment has faded, questions and concerns continue to linger months into the cleanup that led authorities to conduct a "controlled release" of vinyl chloride. Some residents say they still fear that the water, air, soil and surfaces in the village are not safe.

The derailment caused widespread problems in East Palestine that also affected neighboring communities in Pennsylvania. No one was injured during the incident, but in the days afterward, residents reported they had developed rashes, sore throats, nausea and headaches, and linked the symptoms to the chemicals released after the train derailed.

"People are still not back in their homes, they are actively being exposed, they are still sick," said Jami Wallace, who along with other residents Wednesday night wore a shirt that read, "We the People Have Had Enough."

Homendy and the board's three other members took questions from residents who expressed distrust of officials' accounts, and anger — including at the railroad company's efforts to remediate the impact of the spill. NTSB officials said they couldn't answer residents' questions focused on legal and environmental concerns, which are outside the panel's jurisdiction.

The 1.8-mile-long train derailed on the night of Feb. 3, when 38 out of 149 train cars heading from Illinois to Conway, Pa., went off the tracks and caused an explosion that sent flames high into the air and a dense cloud of smoke across the landscape. Twenty of the derailed rail cars contained hazardous materials, including vinyl chloride — a carcinogen that is highly flammable.

Officials evacuated residents and authorities performed a "controlled release" and burn-off of hazardous chemicals from derailed train cars to avoid what they said could be a potential catastrophic explosion. Days later, residents were told that it was safe to return to their homes following air tests conducted by the Environmental Protection Agency. But some residents have remained skeptical of the test findings.

Some still question how safe their community is, whether the air and water tests are valid, and the potential long-term health effects.

About a mile from the high school, crews continue remediation work on the tracks. Some roads remain closed, affecting traffic in a residential and commercial corridor of the town. Heavy machinery was visible on the tracks Wednesday, while dump trucks drove in and out of areas closed to the public. Crews with HEPACO, an environmental and emergency services company, were on-site.

Norfolk Southern, the Atlanta-based railroad company, said it has spent more than $62 million in remediation and community support since the derailment. That includes $17 million in assistance to nearly 10,000 families, the company said. The railroad said it continues to do routine monitoring of the air quality and is creating a training center for first responders to prepare them for future rail safety emergencies.

Norfolk Southern said it has invested $7.7 million on initiatives for first responders and provided $7.5 million to support nearby communities across the Pennsylvania state line. The company faces multiple lawsuits from residents, the state and the U.S. Justice Department.