Spoiled milk was the likely vehicle that sickened inmates and employees at eleven state prisons between May 16 and 26. Over 1,600 inmates reported gastrointestinal symptoms prompting an investigation by the state health department. While, bacteria was never isolated from the milk samples, prisoner stool samples contained Campylobacter jejuni. A case-control study of the prisoners found that consumption of milk increased the risk of illness eleven times. The milk was supplied by the Deuel Vocational Institution farm in Tracy, CA. Environmental swabs from the processing plant showed no bacteria, and the facilities appeared to adhere to health and safety standards. Campylobacter jejuni was isolated from farm samples. Three flush-alley water samples grew Campylobacter jejuni that matched the outbreak strain. The dairy halted production for inspection on May 19, and they recalled all the milk produced between May 8 and 18. This milk was tested and found to have higher levels of bacteria, but the testing laboratory was unable to identify the bacteria from processed milk.