Independent counsel Lawrence E. Walsh has received a report, allegedly given short shrift at the Justice Department last fall, of a connection between a Colombian cocaine kingpin and Southern Air Transport, the former CIA airline involved in the Iran-contra affair.

According to informed sources, a witness told the Federal Bureau of Investigation last summer of having seen a cargo plane with Southern Air markings being used for a guns-for-drugs transfer at an airfield in Barranquilla, Colombia, in 1983.

Jorge Ochoa, reputedly leader of the Colombian cocaine smuggling ring known as "the Medellin cartel," was directly in charge of the operation, according to U.S. officials and others familiar with the individual's statements.

The informant told investigators that crates of guns were unloaded from the cargo plane and packages of cocaine stored aboard, the sources said.

Southern Air is under investigation for its role in ferrying weapons to Iran and to U.S.-backed rebel forces in Nicaragua. The FBI began that inquiry last Oct. 6 after an unmarked C123 cargo plane financed and serviced by Southern Air was shot down in Nicaragua while ferrying guns to the rebels.

The same C123 had previously been owned by Barry Seal, a pilot for the Ochoa family whose work as a DEA informant in 1984 led to federal indictments of the purported cartel leaders. Seal, who nicknamed the plane "The Fat Lady," was murdered in a parking lot in Baton Rouge, La., last February, allegedly on cartel orders.

The informant in the 1983 Barranquilla incident, which did not involve the C123, first volunteered that information to the FBI last July but, as a walk-in, apparently attracted little notice until the case came to the attention of Sen. John F. Kerry (D-Mass.).

Kerry met with Assistant Attorney General William Weld, head of the Justice Department's Criminal Division, on Sept. 26 to discuss what the informant might say if given federal protection.

Kerry followed up with a formal proffer Oct. 7, two days after the C123 downing, but, according to a letter he wrote later that month, he was told that "the Justice Department considers the information provided to date insufficiently detailed."

In a letter to the Justice Department Oct. 22, Kerry noted that "the informant met regularly with the FBI for months prior to contacting us."

In meetings with his staff, Kerry also said, "the informant has given us significant information regarding connections between narcotics trafficking and foreign governments, corruption involving past and present U.S. government officials in connection with narcotics trafficking and an eyewitness account of weapons and narcotics trafficking involving Southern Air Transport."

In addition to the Barranquilla incident, sources said, the witness told in less detail of another visit to Barranquilla in October 1985 by a Southern Air plane.

The personal flight logs of Wallace B. Sawyer, copilot killed in the C123 crash Oct. 5 and who worked for Southern Air, indicate two visits to Barranquilla in October 1985 aboard a Southern Air L382 cargo plane.

Officials of the Miami-based airline have told reporters: "We have never done anything illegal."

Initial disclosure of the informant's claims was made by the Miami News Oct. 30 in a report headlined "Drug Smuggler Fingers Southern Air Transport."

That day, Associate Attorney General Stephen S. Trott, acting at the behest of Attorney General Edwin Meese III, told FBI Director William H. Webster to delay the bureau's investigation of Southern Air.

Asked for comment Saturday, Justice Department spokesman Patrick Korten dismissed the thought that the Miami News report might have been a factor in delaying the Southern Air inquiry.

"There is no connection whatsoever," he said. He said the delay was occasioned "exclusively and solely" by a phone call, also Oct. 30 as Korten recalled it, from Vice Adm. John M. Poindexter, then national security adviser, to Meese.

Justice Department officials have said Poindexter requested the delay because Southern Air was involved in "a sensitive mission" in the Middle East at the time -- ferrying a new load of weapons to Iran.

Delivery took place on Oct. 26 and 27, and American hostage David P. Jacobsen was released in Lebanon a few days later.

Negotiations for the release of other U.S. hostages broke down soon after that. But the delay in the FBI's Southern Air investigation continued until Nov. 26, the day after Meese publicly disclosed the apparent diversion of Iranian arms-sale profits to the contras.

On the day of the Miami News article or the day after it, FBI agents in Miami brought the informant in for a polygraph examination, sources said.

Some sources said the witness passed the test, but Korten publicly disputed that on Saturday. Denying that the test was prompted by the News article, he said it was a consequence instead of Weld's communications with Kerry.

"The results of the polygraph test were inconclusive," Korten said.

"At this point, this individual is not a witness," he added. "An individual can become a witness only if we are able to get an agreement to become a witness and only if we can, in some fashion, corroborate the witness' story." He said neither condition has been met.

Files in the case were turned over to Walsh earlier this month in line with his mandate to investigate provision or coordination of support for the contras, including the activities of Southern Air.

Walsh, in turn, has told the Justice Department that he will send back any cases that he feels are not within his jurisdiction. Asked by a reporter about the Barranquilla incident, he said, "I can't comment."