WASHINGTON — Newly released documents show Watergate Special Prosecutor Archibald Cox expressed "extreme interest" in a 1970s criminal investigation of Yankees owner George Steinbrenner for illegal campaign contributions.

Then-FBI Director Clarence M. Kelley echoed Cox's concern in an Aug. 16, 1973 memo to the bureau's Cleveland office, saying agents needed to make sure the probe received "the same, immediate and preferred handling" as other criminal cases then growing from the Watergate scandal.

The memos were included in a 400-page release Thursday of Steinbrenner's FBI file. Most of the material focused on the Watergate-era federal probe that led to the shipbuilding magnate's 1974 conviction for illegal contributions to disgraced President Richard M. Nixon. There are scant references to Steinbrenner's later pardon by President Ronald Reagan and nothing on his turbulent career as the Yankees' "Boss."

The Associated Press and other news organizations requested the file under the Freedom of Information Act following Steinbrenner's death in July.

"The office of the Special Prosecutor has indicated extreme interest in this matter and requests that the interviews be conducted as soon as possible, and as nearly at the same time as possible," Kelley wrote in the memo on the investigation into Steinbrenner and his American Ship Building Co.

Among other things, the FBI was investigating whether company employees were told they would be reimbursed by the company for campaign contributions, a violation of campaign finance laws.

Steinbrenner was indicted the following year and vowed to prove his innocence in court. But in August 1974, just two weeks after Nixon resigned in the Watergate scandal, the Yankees owner pleaded guilty to two charges in the case and was fined $15,000.

American Ship Building Co. employees told FBI officials in signed statements that they received bonuses around the same time they made donations to Nixon's campaign. The payments varied from $2,800 to $3,500, according to an Aug. 30, 1973 report by the Cleveland office of the FBI.

But the employees claimed the donations "were all of their own desires and in no way were motivated or solicited by George M. Steinbrenner or any other company officials . those interviewed stated that they would have made contributions to the Nixon campaign regardless of the receipt of their bonuses."

One charge that Steinbrenner later pleaded guilty to involved a conspiracy to funnel corporate campaign contributions to politicians. The other accused Steinbrenner of making a "false and misleading" explanation of a $25,000 donation to Nixon's campaign and trying to influence and intimidate employees of his shipbuilding company to give that false information to a grand jury. Steinbrenner could have faced up to six years in prison for the guilty pleas.

Steinbrenner bought the Yankees in 1973, but baseball commissioner Bowie Kuhn suspended him for two years, calling Steinbrenner "ineligible and incompetent" to have any connection with a baseball team.

"Attempting to influence employees to behave dishonestly is the kind of conduct which, if ignored by baseball, would undermine the public's confidence in our game," Kuhn wrote in a 12-page ruling. The suspension was later reduced to 15 months.

Reagan pardoned Steinbrenner at the end of his final term in office.

Steinbrenner told the New York Times in 1988 that he felt badly about the conviction and was willing to bear responsibility for the crimes, but said they happened because he didn't understand what the campaign finance act required of him.