Human rights groups say the use of child labor is widespread in fruit and vegetable fields across the country.
"Americans think of child labor as a problem elsewhere, but in fact we have that problem in our own backyard," said Zama Coursen-Neff of Human Rights Watch, which is conducting its own investigation of child labor practices in the U.S.
"There is child labor in agriculture in almost every state in the United States," she told ABC News.
In North Carolina, Carnegie fellows Stonington and Linsay Rousseau Burnett, of the U.C. Berkeley Graduate School of Journalism, recorded children working in tomato fields in the western part of the state.
The nurse with a migrant health clinic program, Josie Ellis, told the fellows she is concerned for the health of the young children given the widespread use of pesticides in the fields.
"A lot of the chemicals that the kids are around cause respiratory illness, neurologic impairments, contact dermatitis, really severe rashes on their bodies," Ellis said.
The nurse said her complaints to the U.S. Department of Labor office, several hours away in Raleigh, rarely resulted in any action.
"They just don't seem to really care," she said.
The Obama administration's Secretary of Labor, Hilda Solis, promised a crackdown on child labor violations after taking office.
This summer, labor inspectors cited blueberry growers in North Carolina, Arkansas and New Jersey for using children in their fields, with fines averaging $1,100 per child.
While advocates for children welcomed the enforcement efforts, many say the fines levied by the Department of Labor, are so slight they're little more than a slap on the wrist.
"I think it's shameful that our nation tolerates child labor," said Ellis, the North Carolina nurse.
Human Rights Watch investigators say the law needs to be broadened so that it is illegal for children who are 12 and 13 to work in agricultural settings.
"We don't let them work in factories," said Coursen-Neff, "only in agriculture are kids allowed to trade in their health and education."
The executive director of the North American Blueberry Council, Mark Villata, said the industry "does not condone the use of child labor."
But, said Villata, "we cannot control the practices of every one of the more than 2,000 blueberry growers in the United States." He said he believes the ABC News report "represents only a tiny segment of our industry."