DALLAS (AP) - For years, federal agents had received tips alleging undocumented immigrants were working at plants owned by the Pilgrim's Pride Corp., the nation's largest chicken producer. This spring, Immigration and Customs Enforcement agents in Dallas acted on leads that pointed toward two of the company's seven East Texas plants. Undercover agents posing as illegal immigrants infiltrated an alleged network of job-seekers who paid hundreds of dollars for fraudulent identification while those responsible for hiring them looked the other way. By the time the investigation wrapped up in December, agents had arrested 24 people, including: - A Pilgrim's Pride...