Eight months before Marine Lt. Col. Oliver L. North's activities on behalf of the contras were exposed, the Justice Department had evidence of his possible illegalities but did not investigate aggressively, the U.S. attorney in Miami has testified.

FBI agent Kevin Currier, in now-released testimony to Congress, said that U.S. Attorney Leon Kellner's office was "dragging its feet" on questions about secret arms shipments to the Nicaraguan contras.

On Kellner's order, according to the testimony, his Miami investigation into the matter was sidetracked for six months in 1986. And Assistant U.S. Attorney Jeffrey Feldman, a Kellner aide, quoted him as saying "politics are involved."

Kellner, in a deposition to House investigators also released yesterday, denied any political motives and said he did not order a probe of North's activities because he wanted to focus his gun-running investigation around Florida developments and it already was legally complex.

"We were still questioning whether or not there was a crime involved" in the gun-running from Florida to the contras, Kellner said in an April 30 statement to the House Iran-contra committee, made public by Sen. John F. Kerry (D-Mass.).

The testimony of Kellner, three other Justice Department attorneys and the FBI investigator presents new evidence that senior law enforcement officials had early indications of North's activities on behalf of the contras.

The testimony also reveals for the first time the frustration experienced by the junior attorney and investigator working on the case over the unwillingness of their superiors to pursue it aggressively.

Another assistant U.S. attorney, David Liewant, has alleged previously that he was in a meeting at which Kellner said he had been instructed by superiors in Washington to stall the investigation.

Kerry, a Senate Foreign Relations Committee member whose office began a parallel gun-running investigation in early 1986, said yesterday, "These depositions raise some serious questions as to why the Justice Department failed to follow through and investigate the information it had in Florida."

Kellner, top aide Richard Gregorie and Deputy Assistant Attorney General Mark M. Richard, who monitored the Miami probe from Washington, denied that top Justice Department officials made any attempt to interfere.

Attorney General Edwin Meese III, whose aides also kept tabs on Kellner's probe and reported on its status to the National Security Council, appeared for the seventh time yesterday before the grand jury investigating secret U.S. arms sales to Iran and the diversion of profits to the contras.

The jury, convened by independent prosecutor Lawrence E. Walsh, has been looking at the activities of North, who was fired from the NSC staff, and his former supervisor, retired Navy rear admiral John M. Poindexter.

During the 1986 delay by Kellner's office, North continued to manage the shipment of arms to the contras despite a congressional ban on official U.S. military aid to the rebels fighting Nicaragua's government.