A federal prosecutor told the jury in the immigration trial of US poultry processor Tyson Foods that the trial was about “corporate greed”.

Tyson and three of its managers are accused of conspiring to smuggle illegal immigrants from Guatemala, Honduras and Mexico to work in 15 poultry processing plants in nine states.

In his opening statement at the trial, Assistant US Attorney John MacCoon said he would play five hours of tape-recorded conversation and air witness testimony about the alleged smuggling.

A lawyer for Tyson argued that company executives were unaware of any smuggling operations and tried to maintain a legal staff amid a tight 1990s labour market. When Tyson uncovered illegal aliens working at some of its plants it informed government immigration officials by letter, but got no response.

"No member of (Tyson's) senior management ever violated immigration laws or encouraged employees to do so," Tyson attorney Tom Green was quoted by Reuters as saying. Yet "it's obvious that following the law is no guarantee that no illegal aliens will be hired."

A spokesman for Tyson, Gary Mickelson, said of the undercover tape-recordings: "The tapes make it clear that the few individuals involved went to great lengths to make sure that no one at corporate headquarters knew what was going on. The company has very strict hiring policies. When the company did find out about the violations of company policy, the employees involved were dismissed."