The FBI has started a new investigation of Secretary of Labor Raymond J. Donovan as a result of fresh allegations concerning his conduct as a New Jersey construction company executive.

"It's in the . . . area of kickbacks," one source said. Another source suggested it would be more accurate to describe the inquiry as involving an alleged company payment to a labor leader.

The investigation amounts to a "preliminary inquiry" under the Ethics in Government Act and is geared toward determining whether a special prosecutor should be appointed to continue pursuing the case.

Under the act, the attorney general must conduct a preliminary investigation whenever he receives "specific information" that any high-ranking federal officer or campaign official designated by the statute has violated any federal criminal law other than a petty offense.

FBI agents reportedly started work within the last 10 days and have been conducting interviews in the New York-New Jersey area.

The Justice Department refused all comment, both when asked if new allegations concerning Donovan were under investigation and if the department was considering appointment of a special prosecutor.

"We aren't going to get in the business of commenting on special prosecutors," said department spokesman Tom DeCair. "We rarely, if ever, comment on investigations."

Donovan was not available for comment.

The inquiry at this point is "not meant to be thorough" and is expected to be concluded shortly, well within the 90-day limit prescribed by the ethics in government law.

"It's a reasonably specific allegation," one source reported. "We're not talking about hundreds of thousands of dollars here."

Before his Senate confirmation last February, Donovan was under intensive FBI investigation concerning more than a dozen allegations that he and his New Jersey construction company had links to organized crime.

Donovan weathered the storm, assailing his chief accuser as "murdering slime" and protesting that his nomination had been clouded by an unfair presumption of guilt that he called "the New Jersey syndrome." He declared that the accusations were "unfounded, scurrilous and groundless."

The FBI reported it was unable to corroborate any of the reports despite more than 100 interviews and lengthy inspection of corporate records at Donovan's firm, the Schiavone Construction Co. of Secaucus, N.J.

There were some post-confirmation complaints by Democratic members of the Senate Labor Committee that the bureau's investigation had some major shortcomings, but the grumbling dissipated after a committee staff review.

The current investigation was triggered, sources said, when a new informant stepped forward. Officials evidently concluded they could not ignore the latest assertions.

According to the legislative history underpinning the ethics act, the "specific information" needed to trigger the process includes all allegations of wrongdoing except generalized allegations with no factual support. For instance, according to a recent report by a Senate Government Operations oversight subcommittee, "a solitary phone call claiming that a named Cabinet officer is 'dishonest' would not trigger a preliminary investigation."

Upon completion of the preliminary inquiry, which "must not reach the dimensions of a full-blown investigation," the attorney general must submit a report to the special-prosecutor division of the U.S. Court of Appeals here.

Three courses of action are possible:

The attorney general may find that the matter is "so unsubstantiated that no further investigation or prosecution is warranted."

The attorney general may find that further investigation or prosecution is warranted. If he does, he must apply to the court for appointment of a special prosecutor.

The attorney general may make no determination at the conclusion of the 90-day period following receipt of the allegation. Here again, a special prosecutor would have to be appointed.