The New York Daily News said Tuesday the late Steinbrenner's file showed he passed information on to the bureau between 1978 and 1983, but there were few details on exactly what he told the G-men.
Steinbrenner apparently became an informant after he pleaded guilty to making an illegal contribution to President Nixon's re-election campaign.
His deepest role appeared to be during an undercover investigation in the late 1980s that led to an arrest and conviction, the Daily News said.
The incident was referred to in a letter from Steinbrenner's lawyers to the FBI that said in part he knew "he placed the lives of his family and himself in jeopardy through being involved in a terrorist matter."
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