Flint was just the start.

Thousands of neighborhoods across the country have higher lead poising rates than Flint, Mich., according to a Reuters investigation published today.

The Centers for Disease Control defines high lead content as 5 micrograms or more per deciliter, and 2.5 percent of children under six have elevated rates nationwide. Reuters found nearly 3,000 neighborhoods with double the rates of poisoning found in Flint. Roughly 1,000 neighborhoods had rates that were at least four times higher.

Lead poisoning is tough to find, according to the report. Children aren’t tested often and when they are, the results are reported at the state or county levels, while areas with acute lead poisoning are hidden.

Congress gave Flint $170 million in aid this year, Reuters noted, but the CDC’s budget state lead poisoning aid is a fraction of that. Reuters reporters visited several areas afflicted with high lead levels. They’re often poor and midwestern, like Missouri, where the statewide average is five percent and several areas passed 15 percent.

This data covers less than half the states — only 21 were able to get Reuters the specific data it requested.

Identifying the issue is only one part of the problem. When pipes and old buildings are poisoning the population, fixes can be tough. For a case study, revisit our reporting from Flint by clicking the audio player below.