DETROIT (AP) – The city of Flint, Michigan, is getting heavy state and national attention and much-needed assistance as it deals with a drinking water crisis that began after officials switched water source in 2014 while under state financial management, and the tap water became contaminated with lead.

Michigan National Guard leaders began arriving in the city Wednesday to help distribute bottled water, filters and other supplies. The Federal Emergency Management Agency also approved a request by Michigan Gov. Rick Snyder, whose administration has come under fire for how it handled concerns about the water, to coordinate a recovery plan.

READ MORE: What Is The Best Sunscreen For Me? Environmental Working Group Releases Annual Guide

It’s yet another challenge for a city of 99,000 people beset by numerous auto factory closures and thousands of job losses over the decades, and where about 40 percent of the population lives in poverty.

Here are some questions and answers on how Flint got here, where things stand and what’s next:

When and why did Flint switch its water source?

Flint had long received its water from Detroit’s massive system but officials complained about the rates. For years, officials in Flint and surrounding Genesee County discussed creating an independent system – along with a separate pipeline to Lake Huron. In April 2014, Flint left Detroit’s system and joined the regional effort, tapping into the Flint River as its primary source until the pipeline would be completed. It was seen as an effort to save money while the city was led by an emergency manager appointed by the Republican governor.

What happened?

Right away, residents complained about the taste, smell and appearance of the water, and reported adverse health reactions, but officials said state tests met federal safety guidelines. A General Motors plant stopped using the water, saying it was rusting its parts. Subsequent independent tests found children with elevated levels of lead in their blood and it was determined that the highly corrosive river water was drawing lead from aging pipes. State officials initially challenged or dismissed those findings, and, for more than a year, lead leached into homes. Lead exposure can cause behavior problems and learning disabilities in children, and kidney ailments and other issues in adults.

When did the state acknowledge the problem?

READ MORE: Parole Denied For Don Miller Who Killed 4 Women In Lansing In The 1970s

County health officials declared a public health emergency Oct. 1, and the next day Snyder announced $1 million for home water filters. A week later, he called for Flint to return to Detroit’s water system, said water at schools would be immediately tested and pledged millions more in aid. That month, he also said a task force would review how everything had been handled and offer recommendations.

Why did it take so long?

Snyder said he sought answers earlier last year from state environmental officials but action was delayed when his office received inaccurate information. The state auditor general and the task force faulted the Department of Environmental Quality for not requiring Flint to treat the river water for corrosion and for belittling the public’s fears. Former DEQ Director Dan Wyant resigned last month. Critics have argued Snyder should have acted sooner as the person ultimately responsible, a point he recently acknowledged and for which he apologized.

Efforts also intensified with the November election of Mayor Karen Weaver over the incumbent, who had blamed state and federal officials. Weaver declared a state of emergency, which led the county and ultimately the state to do the same last week.

What’s next?

Snyder pledged this week that officials would contact every household in Flint to check whether residents have bottled water and a filter and want to be tested for lead exposure while his administration works on a long-term solution. Nearly 30 Guardsman are expected to be in place by Friday, enabling American Red Cross volunteers to join door-to-door efforts. The Federal Emergency Management Agency also has approved Snyder’s request to coordinate a recovery plan.

Snyder said that since October, about 12,000 filters have been distributed and roughly 2,000 blood tests have been done – uncovering 43 cases of elevated lead levels – but the actions aren’t “good enough.” It can sometimes be difficult to gauge the effects, which health officials say can take years to fully manifest.

MORE NEWS: Michigan Court Seeks More From Whitmer About Abortion Ban Challenge

© Copyright 2016 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.