One morning in 2019, an auditor arrived at a meatpacking plant in rural Minnesota. He was there on behalf of the national drugstore chain Walgreens to ensure that the factory, which made the company’s house brand of beef jerky, was safe and free of labor abuses.He ran through a checklist of hundreds of possible problems, like locked emergency exits, sexual harassment and child labor. By the afternoon, he had concluded that the factory had no major violations. It could keep making jerky, and Walgreens customers could shop with a clear conscience.When night fell, another 150 workers showed up at the plant. Among them were migrant children who had come to the United States by themselves looking for work. Children as young as 15 were operating heavy machinery capable of amputating fingers and crushing bones.Migrant children would work at the Monogram Meat Snacks plant in Chandler, Minn., for almost four more years, until the Department of Labor visited this spring and found such severe child labor violations that it temporarily banned the shipment of any more jerky.In the past two decades, private audits have become the solution to a host of public relations headaches for corporations. When scandal erupts over labor practices, or shareholders worry about legal risks, or advocacy groups demand a boycott, companies point to these inspections as evidence that they have eliminated abuses in their supply chains. Known as social compliance audits, they have grown into an $80 billion global industry, with firms performing hundreds of thousands of inspections each year.But a New York Times review of confidential audits conducted by several large firms shows that they have consistently missed child labor.Children were overlooked by auditors who were moving quickly, leaving early or simply not sent to the part of the supply chain where minors were working, The Times found in audits performed at 20 production facilities used by some of the nation’s most recognizable brands.Auditors did not catch instances in which children were working on Skittles and Starburst candies, Hefty brand party cups, the pork in McDonald’s sandwiches, Gerber baby snacks, Oreos, Cheez-Its or the milk that comes with Happy Meals.In a series of articles this year, The Times has revealed that migrant children, who have been coming to America in record numbers, are working dangerous jobs in every state, in violation of labor laws. Children often use forged documents that slip by auditors who check paperwork but do not speak with most workers face-to-face. Corporations suggest that supply chains are reviewed from start to finish, but sub-suppliers such as industrial farms remain almost entirely unscrutinized.The expansion of social compliance audits comes as the Labor Department has shrunk, with staffing levels now so low that it would take more than 100 years for inspectors to visit every workplace in the department’s jurisdiction once. For many factories, a private inspection is the only one they will ever get.Auditors for several firms said they are encouraged to deliver findings in the mildest way possible as they navigate pressure from three different sources: the independent auditing firms that pay their salaries; corporations, such as Walgreens, that require inspections at their suppliers; and the suppliers themselves, which usually must arrange and pay for the audits.The auditor who looked at the Minnesota jerky factory for Walgreens was Joshua Callington. He has conducted more than 1,000 audits in the past decade.“If audits are done correctly, the world could be a better place,” he said. “Bettering the lives of workers is what these audits are supposed to be about.”But more and more, he said, each audit had begun to feel like a struggle between wanting the truth and trying to avoid conflict.He had not seen any child labor in the Minnesota factory. To keep to his work schedule, he had to leave for his next audit at 4 p.m., long before the late shift arrived. Spotting problems had also led to tension between Mr. Callington and his employer, UL Solutions, which began as a safety testing business and expanded more than two decades ago into social compliance audits. The company took in $2.5 billion in revenue last year and is on the cusp of an initial public offering.What Mr. Callington saw as a commitment to his job, his firm seemed to see as overzealousness.“The assessment is not meant to be a policing effort,” the UL Solutions employee handbook says.After Mr. Callington failed three Walgreens suppliers in 2017 and 2018 for abusive working conditions, the chain complained about his communication style and asked for him to be taken off its account. UL put him on a remediation plan for about a year. (Walgreens declined to comment on the incident, but said it only rarely asks for auditors to be removed. In response to questions about the Monogram factory, the company said it had cut ties with the supplier. Monogram said it is now using stronger age-verification procedures.)This spring, Mr. Callington flagged labor issues involving adult migrant workers at a warehouse that supplies Costco’s potatoes. The plant’s management complained that he was demanding and argumentative, and his supervisor barred him from returning. Mr. Callington believed that the supplier objected to his finding 21 violations when the previous audit had found none. UL Solutions declined to comment on either incident.The supervisor said Mr. Callington would have to complete a series of customer service trainings, and concluded with an inspirational quote that he attributed to the poet Maya Angelou.“‘People will forget what you said. They will forget what you did. But they will never forget how you made them feel,’” he wrote in an email. “Keep this in mind as you are interacting with our clients during your audits.”Night Shifts, Daytime AuditsIn dozens of interviews, auditors said that sometimes their firms provide little more than a veneer of compliance for global corporations, which overstate how rigorously they review sprawling supply chains.Auditors typically start their inspections in the morning and stay for about seven hours, even at 3,000-person factories that operate around the clock. In practice, this means that late afternoon and night shifts, where child labor violations most often occur, are almost never seen.This year, the Department of Labor imposed a $1.5 million fine against Packers Sanitation Services, which provides cleaning crews to slaughterhouses. Investigators found that the company was employing more than 100 children, including 13-year-olds, to clean back saws and head splitters overnight.These plants had been supplying McDonald’s and Costco for years, and the corporations required regular audits. Some of those auditors noted that there was a large night shift run by the sanitation company, but said they had not been able to observe any of the workers. One auditor who was checking a Nebraska plant for Costco’s Kirkland brand beef spoke with 20 out of 3,500 workers — as is standard in much of the industry — and left at noon, an inspection showed. In another audit at the same plant, the inspector left at 1:30 p.m.Costco and McDonald’s said in statements that they were strengthening their auditing standards. Packers said it had improved age verification of its workers.Even if auditors had stayed later at the plants, they might not have been able to talk privately with the migrant child workers, who largely speak Spanish or Indigenous languages of Central America. Auditing firms rarely provide interpreters.“You’re supposed to ask another worker to translate. But you’re trying to unearth something that people aren’t trying to yell from the rooftops,” said Juanita Sanchez-Sevilla, a Spanish speaker who has been conducting audits since the 1990s, including for the leading firms Intertek and Bureau Veritas. “If you look at the upper echelons of the industry, they’re all white.”In the absence of in-person interviews, auditors rely on paperwork. But children use forged documents. This summer, for instance, a 16-year-old from Guatemala was killed while cleaning a Mississippi slaughterhouse that supplies Chick-fil-A. His documents said he was in his 30s. In a statement, Chick-fil-A said it was reviewing how it investigates violations at plants.Duvan Perez, 16, was killed this summer while cleaning a Chick-fil-A supplier in Mississippi. Research has shown that outside audits are less conclusive than companies suggest. A 2021 analysis of 40,000 audits by a Cornell professor found that nearly half had relied on forged or dubious documents. An earlier study that explored the industry’s financial conflicts of interest found that auditors report fewer violations when factories are paying the bill.In a…