New York (Reuters) – A team of Reuters reporters on Monday won a George Polk Award for reports that revealed the widespread use of child labor among suppliers to Hyundai Motor Co in the U.S. state of Alabama.

The series of stories, “Undocumented and Underage,” has prompted at least 10 probes by U.S. and Alabama authorities into suppliers of Hyundai and sister brand Kia. The reporting was carried out over more than a year by journalists Joshua Schneyer, Mica Rosenberg, Kristina Cooke and colleagues.

The Polk jury, awarding the prize in its “state reporting” category, said Reuters “sparked increased scrutiny from federal and state agencies and led Hyundai to demand more accountability from its suppliers.”

The recognition, among the top honors in U.S. journalism, is administered by Long Island University and emphasizes investigative reporting in the public interest.

In a series of in-depth reports and exclusives, the reporters showed that migrant children as young as 12 worked in dangerous Alabama factories to build parts for the Korean automakers.

After Reuters’ July 2022 story revealed the use of child workers at a parts maker majority-owned by Hyundai, federal and state authorities found and rescued minors from another Hyundai supplier and fined that company and one of its labor contractors.

The stories led a group of 33 members of Congress this month to urge the U.S. labor secretary to seek strong penalties against those responsible for hiring the underage workers. Also in February, Hyundai itself said it was in discussions with the Labor Department to resolve concerns about the child labor.

To uncover the infractions, Reuters reported in low-income immigrant communities across Alabama and knocked on doors at trailer parks, town halls and employment agencies. The reporters interviewed migrant families, pastors, social workers, police and school officials, and spoke with more than 100 factory workers.

After discovering that staffing agencies hired child workers for employment in Alabama poultry plants, they learned that migrant minors were also building parts for Hyundai and Kia. Both companies have said they don’t tolerate child labor and are taking measures to ensure underage workers don’t find their way back into their supply chains.

Other winners recognized for a Polk Award on Monday included The New York Times, honored for its coverage of the war in Ukraine, and Politico, for exclusive reporting of a draft opinion at the U.S. Supreme Court that overturned decades of precedent on abortion rights.

(Writing by Paulo Prada. Editing by Michael Williams.)