Erin Brockovich, one of the nation’s most famous environmental activists, hosted a town hall at the East Palestine High School on Friday evening to discuss issues surrounding the Norfolk Southern train derailment earlier this month.

Erin Brockovich spoke to about 2,500 people and 100 reporters who filled the auditorium and two gymnasiums at the high school, KTLA sister station WKBN reports.

Her message to East Palestine? Stick together and demand answers.

From the outset, she said she planned to tell the community what they needed to hear, no matter how disconcerting.

“You want to be heard, but you’re going to be told it’s safe, you’re going to be told not to worry,” Brockovich said. “That’s just rubbish, because you’re going to worry. Communities want to be seen and heard.”

Concerns over the Feb. 3 derailment began mounting almost immediately after the crash. Mangled train cars were said to have left a half-mile trail of burning material which sent smoke billowing into the sky. As fears grew about a potential explosion, officials had the area evacuated and opted to release and burn toxic vinyl chloride from five rail cars, sending flames and more black smoke into the air.

Concerned locals had later made claims of their pets becoming sick, or that they noticed dead fish turning up in the nearby creek. Some also complained of headaches.

Brockovich, who gained fame and was portrayed in a film for battling Pacific Gas & Electric Co. over groundwater contamination in Hinkley, California, told the audience to fight for recognition and trust their instincts.

“These chemicals take time to move in the water. You’re going to need groundwater monitoring. People on well water: You really need to be on alert. They’re going to need to implement soil vapor intrusion modeling. Believe us. It’s coming,” she said.

As a show of support, Brockovich introduced mothers from Flint, Michigan, to the crowd. She also advised the people of East Palestine to band together to make their voices heard.

“You start getting 50 and 100,000 pissed off moms together — I’m telling you right now: Things change,” Brockovich said.

Many of the attendees said they were unsure of whether they should continue residing in East Palestine, fearing for their long-term health.

Brockovich advised the crowd to journal, and to document what they’re seeing. She also told attendees they should want to know the “worst case scenario” to be better prepared, and to protect themselves.

“You have the ability to become — and you will become — your own critical thinker. You will vet information, you will ask questions, you will demand answers. You will listen to that gut and that instinct that will keep you connected as a community,” Brockovich said. “Don’t let what’s happened here divide you.”

“Unfortunately, this is not a quick fix,” she also said at one point during the evening. “This is going to be a long game.”

Attorney Mikal Watts, who also appeared at the town hall, urged attendees to get their blood and urine tested promptly, saying the results could help establish whether they had been exposed to dangerous substances. It could also be helpful if they choose to pursue legal action at a later date, he said.

“The court of public opinion and a court of law are different,” he said. “We need evidence.”

The Associated Press contributed to this report.