A filmmaker who went to Nicaragua to make a documentary said Thursday he became an undercover operative for a Texas law firm that was suing Dole Foods on behalf of purported banana plantation workers who claim they were left sterile by pesticide exposure.

Jason Glaser testified about his transformation into a secret sleuth, saying he told none of the people he interviewed in Latin America about his dual role.

He was called to the witness stand by attorney Steve Condie, who represents six men claiming they were left sterile by pesticide exposure while working on Dole banana plantations from 1970 to 1980.

Dole investigators uncovered evidence that some Nicaraguans suing the company had lied, saying they were sterile when they had fathered children and vowing they worked on banana farms when they did not.

The first trial on the issue ended in 2007 with jurors awarding $2.3 million to Condie's clients. Dole is seeking to overturn the verdict. A second similar case was dismissed after testimony about fraud.