From Mexican immigrants picking mushrooms in a dank Pennsylvania cinderblock box, to Chinese laborers toiling in overheated New York sweatshops, child labor in its most oppressive forms shows up in many states.

Those states have unique problems uncovering and prosecuting violators of child labor laws.

Some state laws governing child labor are vague and difficult to enforce; other states lack resources or commitment to pursue reports of children working illegally. The variations can be dizzying. Some state child-labor laws are more stringent than federal laws, others more lenient.

In some cases, officials battle ingrained traditions that force children into early employment. In other cases, young workers bring home a significant portion of the family's income. Their money puts bread on the table.

More than two dozen AP reporters and photographers worked for five months to investigate child labor in 16 states.