A federal grand jury investigating the Iran-Contra affair has named former National Security Council secretary Fawn Hall, an ex-NSC official and a former CIA agent as unindicted co-conspirators, it was reported Saturday.

The unexpected move, which has been kept secret under court seal, will allow independent counsel Lawrence Walsh who is investigating the case to use the testimony of Hall, former NSC official Robert Earle and ex-CIA agent Joe Fernandez against all four defendants, the Los Angeles Times said.The defendants former NSC aide Lt. Co. Oliver North, former NSC adviser Vice Adm. John Poindexter, Maj. Gen. Richard Secord and arms dealer Albert Hakim face allegations of conspiring to divert profits from the sale of arms to Iran to the Nicaraguan Contra rebels.

"By using statements from (Hall) and others as witnesses, when they come in as co-conspirators, it tarnishes all the others in the case," one source close to the investigation told The Times. "The statements can be used against all four conspirators."

Testimony from Earle could be particularly damaging to North because he was one of a handful of people who were aware of the funds diversion and often passed messages among principals in the affair, including Poindexter and Secord.

Hall had admitted removing classified materials from the NSC while she was North's secretary, and Earle has admitted shredding documents for North.

Walsh has granted immunity from prosecution to Hall and Earle, but Fernandez could still face charges in the case, a source told The Times.