Hundreds of Flint residents on Tuesday packed into a ballroom at the University of Michigan-Flint, hoping to receive answers from a legal team representing potentially thousands of plaintiffs in several lawsuits filed over the water crisis in Flint, where financial damages may exceed $1bn.

Residents lobbed stories back and forth of severe illness, of emotional distress due to the unfathomable circumstances, of a blatant mistrust of a government that, time and again, reassured them the water was safe to drink.

Jim O’Connor, 47, said he moved last June into an apartment in Flint with his 16-year-old son, James. Concerns from residents over the city’s water quality were prevalent at the time, yet the apartment’s property manager never discussed the potential harm flowing out of their faucet, he said. So O’Connor and his son continued to drink the water. Ever since, he said, his son’s grades have fallen.

“I found out about [the water contamination] when the governor came on the news in October,” O’Connor said. When his apartment’s water was finally tested, the lead levels exceeded federal action limits.

“I’m disabled, so moving is really not an option,” he said. “So how I can make it so I can live in the city with this?”

At least nine lawsuits have been filed in federal and state court since last fall after high levels of lead leached into the water supply, with a potential financial liability of $1.25bn for the state and the engineering firm hired to advise Flint on its water treatment plant. Many of them are class action suits with potentially thousands of members.

While the state continues its efforts to aid Flint residents with bottled water and filters, the bevy of cases cover an array of problems that have been linked to the water crisis – from property value loss to legionnaires’ disease to severe post-traumatic disorder.

The city’s drinking water became contaminated in April 2014 after Flint, operated at the time by an emergency manager appointed by the governor of Michigan, Rick Snyder, switched its drinking water source to a corrosive local river. Flint was not required by the state to use anti-corrosion agents to treat the river water, allowing lead and other contaminants to leach from pipes and flow into households. Lead is a neurotoxin known to cause mental and physical disabilities.

“[State officials] need to clean up what they messed up,” said attorney Trachelle Young, a Flint resident herself.

The lawsuits take aim at government officials, the engineering firm hired to prepare Flint’s water plant, and a local hospital linked to a legionnaires’ outbreak. Nearly a dozen federal, state and local investigations are ongoing. An inquiry launched last month by the office of Michigan’s attorney general, Bill Schuette, could produce additional restitution for Flint residents, investigators say, if it is warranted.

“Every week we’re learning of new types of medical conditions that people have been diagnosed with, that have something or other to do with exposure to the neurotoxins in the water,” said attorney Julie Hurwitz, one of several members of the legal teams in three separate class action suits.

Hurwitz said it was too early to calculate potential financial damages for class members, but another attorney on the case told the Guardian in December it “could reach $1bn”. Hurwitz said more than 5,000 Flint water users have been contacted about the case.

Experts and plaintiffs’ attorneys have expressed hesitation over lawsuits filed against state departments and officials, saying the chance of success will be hindered by the legal doctrine of “sovereign immunity”, which means states cannot be held legally responsible except in special circumstances.

But Michael Pitt, co-counsel in the cases with Hurwitz, said he believes the attorneys have a solid legal theory that renders governmental immunity irrelevant. The federal lawsuit, he said, claims Governor Snyder along with several state officials, violated the due process of Flint residents.

“If there’s a constitutional violation, the governmental immunity does not apply,” Pitt said. “It just does not apply. So we’ve filed a case in federal court … alleging a due process violation that the state of Michigan and its agents created a dangerous condition, and that the state and its actors are liable for the damages caused by this constitutional violation.”

The governor’s office did not respond to a request for comment. A spokesperson for Michigan’s attorney general declined to comment, citing the pending litigation.

Separately, a $100m lawsuit has been filed on behalf of several families seeking damages for victims who contracted legionnaires’ disease after the water source switch. State and county officials have been heavily criticized for knowing of a legionnaires’ outbreak over a year before it was made public.

One of the plaintiffs treated at McLaren Flint hospital, Debra Kidd, entered the facility on 25 June, complaining of a headache, according to the complaint filed against the medical center and several state environmental officials. Kidd was treated and discharged the same day.

But two days later, the complaint continued, Kidd was admitted to a separate hospital and diagnosed with legionnaires’ disease. A week later, she was dead.

A hospital representative declined to comment on the lawsuit, but said in a statement: “McLaren Flint has consistently followed all statutory regulations and notification requirements … the water at McLaren Flint meets safety and quality standards.”

Patricia Dunning’s family members began experiencing health problems soon after the water source switch, she said. Compounding matters, a recent test showed the lead level in water at her home was still four times higher than statutory limits.

“We’re sticking to straight-up bottled water because I cannot do it,” said Dunning, 40, as she waited to meet officials from local advocacy groups who offered help. “I don’t believe them no more.”

Albert Harris, a Flint native, said the city won’t be relieved until its entire water system is overhauled. “You’ve got to switch everything for it to be clean,” Harris said. The 56-year-old lifted his pant leg to expose a rash that, he said, broke out after Flint began using the local river. Despite several doctor appointments and treatments, the festering blotch remains.

Listening to the class action attorneys introduce themselves, Harris said: “They’re talking about what they’re going to do, how they want to fight for us, to get our justice. But it’s not only just for us, it’s for our generation to come … what about their justice?

“Of course, we’re concerned about ourselves. But, the main thing is, if we don’t stop this now, we ain’t gonna have a future.”