When U.S. Customs Service agents Louis Smit and John Graham stopped a small fishing boat near Port Mansfield, Tex., in 1988, they confiscated 597 pounds of marijuana and inherited a boatload of trouble.

Smit and Graham had stumbled onto one of the largest drug-smuggling operations in the United States. They could handle that. But what they didn't expect was that their investigation would lead them to allegations that some Customs co-workers in Texas were dirty.

For two years, Smit and Graham say, they suffered repeated harassment from some of their superiors whenever they raised the allegations of corruption. Smit was vindicated in a personnel grievance as a victim of on-the-job harassment because he blew the whistle. Now federal investigators are looking into the allegations of corruption. But the Customs Service still asserts it has no problems in Texas.

The drug ring that Smit and Graham investigated led them to accused trafficker Manuel "Pancho" Jaramillo. On the supply side of the ring were Mexicans tied to the notorious cult murders of 15 people near Matamoros, Mexico, in 1989. On the distribution end of the ring was the Chicago mob.

Soon after Smit and Graham plunged into the Jaramillo investigation, they began getting reports that Customs may have dirty laundry. The reports came from the FBI, which had told Customs of possible internal corruption more than a year earlier, and from the Drug Enforcement Administration and the U.S. attorney's office in Texas.

Smit and Graham reported the allegations to their immediate supervisor. That supervisor backed them, until he was forced to accept a transfer to another state. He would later testify in Smit's grievance hearing that higher-ups in Customs told him his own "job was on the line" and that "the political hammer would fall if these two gentlemen were not shut down from investigating corruption."

Smit and Graham, who had exemplary employment records, saw their job evaluations drop to "marginal." They were denied promotions and finally pulled off the Jaramillo investigation.

Smit took several months off to recuperate from an on-the-job injury, and while he was gone, his superiors tried to stack the deck against him. They accused him of misusing his government credit card and using the Customs express mail account to send his whistle-blowing information to a senator. When Smit came back to work, he was denied overtime pay and not allowed to do investigative work.

Fed up, Smit took his case to the federal Merit Systems Protection Board, which last September ruled that he had been retaliated against for whistle-blowing. Customs has appealed that ruling.

Our associate Dean Boyd has learned that the Office of Special Counsel and the Treasury Department inspector general are investigating the allegations of corruption in Customs, after promptings from Sen. Harry Reid (D-Nev.).

Southwest Region Customs spokeswoman Donna De la Torre told us that Customs' internal investigation had turned up "no substantiation" of the corruption charges. Despite the indictment of Jaramillo and 13 others, the ordeal proved too much for Smit, who last week announced his resignation.