WASHINGTON, UNITED STATES -- The U.S. state of Michigan has agreed to pay some US$600 million to victims of the Flint water crisis, a health scandal that became a symbol of social injustice in America, officials said Thursday.

The settlement could see payments to tens of thousands of people, children and adults alike, who may have ingested lead-tainted drinking water after the city of Flint changed the source for its water system in 2014 to cut costs.

"What happened in Flint should have never happened, and financial compensation with this settlement is just one of the many ways we can continue to show our support for the city of Flint and its families," Governor Gretchen Whitmer said in a statement.

She called the suffering and delays in addressing the problem "unconscionable" and acknowledged the settlement "may not completely provide all that Flint needs."

Napoli Shkolnick PLLC, the law firm representing victims in their lawsuit, said the settlement included the state, Flint city, former state and city employees, and former governor Richard Snyder.

"The Flint community and children have suffered significantly; this settlement is the beginning of the process for healing and supporting this important community," said attorney Paul Napoli.

At least 12 people died after the decaying industrial city switched its drinking water source to the polluted Flint River to cut costs in 2014.

However, officials failed to add corrosion controls to the new tap water source, allowing lead and other contaminants to leach from the city's aging pipe system.

Authorities initially dismissed complaints from residents in the majority black city where many live below the poverty line.

They were eventually pushed to act following national attention and Environmental Protection Agency pressure.

Most of the money is earmarked for children in the city of Flint, who were at greatest risk of neurological and physical harm from lead-tainted tap water.

More than 8,000 children are believed to have consumed lead-contaminated water, and a study found that the proportion of infants and children with high lead levels doubled after the water source switch.

The Washington Post reported that 80 per cent of the settlement would go to residents who were exposed when they were under 18 years old.

The city and state have since taken steps to improve water quality, including reverting to a cleaner water source and a project to replace Flint's ageing pipe network.

Last week the city said it would complete the replacement of lead-tainted pipes by November 30, more than a year later than promised.

Criminal charges filed against eight people accused of playing a role in the health debacle, including high-ranking state officials, were dropped last year.