US President Barack Obama has declared a federal emergency over the Michigan city of Flint's lead-poisoned water crisis that has affected its almost 100,000 residents, with children suffering the most, over almost two years.

The White House on Saturday authorised the Federal Emergency Management Agency to coordinate disaster relief efforts to "alleviate the hardship and suffering" of Flint's residents.

The agency can now provide water, filters, and other necessary items to the city through federal funding.

The announcement came days after Michigan Governor Rick Snyder asked Obama to issue the emergency declaration.

On Tuesday, a class-action lawsuit was launched against the state of Michigan and Snyder for allegedly ignoring Flint's water crisis since it began in April 2014.

The plaintiffs, including residents who have suffered severe illnesses from consuming the toxic water, are also suing Flint's administration as well as other local officials.

The suit accuses the parties of "breaching the contractual obligation" to supply about 30,000 households with potable water.

It also says that residents are still being billed for receiving the contaminated water.

The state administration has denied allegations of negligence.

The crisis erupted after Flint stopped receiving its water supply from the neighbouring city of Detroit due to unaffordable increases in rates and started sourcing from the local Flint River in April 2014 as a cost-cutting temporary measure.

Critics have blamed the state administration for failing to apply essential corrosion control to make the water from Flint River safe for consumption by preventing the antiquated pipelines from leaking lead.

Even though Flint switched back to Detroit's water system, residents say that it is still not drinkable and continue to use bottled water to even bathe and cook.

Snyder called in the country's national guard to help provide potable water for the city's households after declaring a state of emergency over the crisis. He also offered $10M in aid for Flint.

David Murray, press secretary for Snyder, told Al Jazeera the state administration had been "working closely with the city to focus on health issues affecting children and other city residents, and address water infrastructure challenges".

But many say his efforts came too late and there have been recent protests calling for Snyder to resign and face charges over negligence allegations - after an independent investigation by Michigan's Auditor General that found state officials had failed to react to "numerous red flags" since the very early stages of the crisis.

Michigan's Department of Environmental Quality (MDEQ) had reportedly continued to tell Flint residents that the water was safe for drinking despite warnings from local doctors who had found alarming amounts of lead levels in people.

'Cover-up'

Marc Edwards, a water quality expert who is leading an independent investigation into the scandal, told Al Jazeera that the country's Environmental Protection Agency [EPA] also played a role in trying to cover up Flint's crisis.

"EPA knew about this in April last year ... Children continued to drink from the water and they [EPA] did nothing about it until after October," he said.

"The primary blame is clearly the MDEQ, but the EPA played an unconscionable role in covering up what was occurring."

In a statement sent to Al Jazeera, the agency said that it had fulfilled its duty of referring complaints of lead contamination to the MDEQ.

"In February 2015, EPA received a call from a Flint resident expressing concern about the results of a test conducted by the Flint water utility showing high levels of lead in her tap water. EPA immediately conveyed those concerns to MDEQ - because MDEQ is the agency responsible for implementing and enforcing federal drinking water regulations in Michigan," it said.

On Thursday, officials announced a spike in Legionnaires' disease cases that resulted in at least 10 deaths. More than 80 people have contracted the bacterial pneumonia infection since the water crisis began.

Nick Lyon, the director of the Michigan Department of Health and Human Services, has said that about half the cases were connected to Flint water, and half were not.

Dr Mona Hanna-Attisha, a pediatrician conducting research on the health crisis in Flint, told Al Jazeera that her main concern was how thousands of children have been affected, since they are the most vulnerable to the "life-altering and irreversible" damages of lead poisoning.

"First of all, there is no safe level of lead. Our research showed that lead levels doubled in most children screened. In the poorer neighbourhoods, those levels tripled," said Hanna-Attisha.

"Lead poisoning has long-term impacts. It affects your cognitive development, your intelligence, and it is directly linked to violent behaviour."

She added: "The people have been traumatised and lied to for 18 months. They are angry and have little trust in government."