The Illinois Department of Public Health (IDPH) later verified that the outbreak of illness at Laraway Elementary School was caused by the consumption of ammonia-contaminated chicken tenders. The chicken was a Tyson product that had been shipped by Lanter Refrigeration and stored at a Gateway Cold Storage facility near St. Louis, Missouri, which had had an ammonia leak in 2001.
On December 2, 2002, the Food Safety and Inspection Service (FSIS), a branch of the USDA, verified very high ammonia levels in the chicken tenders through its own laboratory analysis. This verified testing conduced by an independent laboratory at the behest of IDPH. The tests revealed contamination of the tenders with ammonia at 500-2,000 ppm. According to the IDPH the legal limit for such concentrations is 15 ppm.
In a rare criminal follow-up, state authorities indicted two Illinois Board of Education members and an operations manager at a food distribution warehouse.
Marler Clark represented 35 children and teachers in claims against the companies responsible for the contamination. The firm resolved the claims in 2004.