The FBI is investigating drug-trafficking allegations in northern Florida involving Panamanian strongman Manuel Antonio Noriega, the second investigation of him by federal agents, government sources said yesterday.

The inquiry, based on confidential informers in Tampa, is focusing on alleged incidents that date back several years, said the sources, who refused to be named.

In Miami, the Drug Enforcement Administration is investigating allegations that Noriega helped launder drug profits and helped protect traffickers' shipments that moved through Panama en route to Miami. That investigation is collecting "every snippet they have on the guy, including accepting bribes for looking the other way on narcotics loads," said an official familiar with the DEA inquiry.

No details could be learned on the allegations being investigated by FBI agents in Tampa. A source familiar with the investigation said only that it was a separate case and "more preliminary."

The expanding drug inquiries into Noriega's activities are further straining relations between the United States and Panama and adding to the pressure on the Panamanian leader to step down. The State Department recently called for new elections and a return to full civilian rule in the country.

Adolfo Arrocha, charge d'affaires for Panama's embassy in Washington, said he knew nothing about the FBI's Tampa investigation. "While it is ongoing, what can I say? We will have to wait to see what comes of it -- if anything," Arrocha said.

Noriega has denied participating in criminal activity.

A Justice Department official said it is unclear whether the two probes will merge, but another source noted that Associate Attorney General Stephen S. Trott found it necessary at a recent department meeting to "referee" investigative actions regarding Noriega by the Federal Bureau of Investigation and DEA.

Some DEA officials, meanwhile, are known to have mixed feelings about their Noriega investigation, contending that he has provided crucial information to the drug agency about traffickers with whom he allegedly has fallen out.

"The DEA would rather live with Noriega, given the alternatives," explained one source familiar with the agency. "If someone doesn't give him the payoff he wants, he sics the DEA on them."

"DEA, especially those on the scene, believe there are more benefits than negatives from dealing with Noriega," one official said.

DEA agents in Miami had been "monitoring" Noriega's alleged drug-related activities for at least two years, one source said, but their work was not regarded as a full-scale investigation until a July 16 meeting at the Justice Department.

At that meeting, presided over by Trott, it was decided to "pull together all we had on him to see if it was prosecutable," the source said. So far, investigators have indicated, no indictments are imminent.