Federal prosecutors have dropped charges against a doctor from the Philippines who went into hiding after being accused of scamming a military health program out of more than $1 million in the 1990s.

The U.S. Attorney's office for the Western District of Wisconsin moved to drop a fraud indictment against Dr. Alberto Marzan last week, saying the "prosecution is no longer viable" because of a lack of evidence. U.S. District Judge Barbara Crabb formally dismissed the case in an order made public Thursday.

Marzan was one of the longest-wanted fugitives in a federal investigation that has uncovered rampant fraud of the U.S. military's Tricare program in the Philippines. Tricare insures current and retired service members and dependents worldwide.

"We believe he was certainly a significant target and had done some pretty significant fraud," assistant U.S. Attorney John Vaudreuil said of Marzan.

But Vaudreuil said the indictment was dropped after a routine review of the office's outstanding fugitive cases. He said witnesses were no longer available, including one who died, and the age and distance of the case would have made a prosecution impractical.

"Given what had happened to our testimony, we didn't believe it was a viable case to prosecute and not fair to bring Dr. Marzan back" to face charges now, he said.

Vaudreuil noted the office had asked authorities in the Philippines to arrest Marzan and bring him to the U.S. under an extradition treaty, but that effort was not successful. He said he had no idea "how he's hiding or how he's successfully hiding" but that appears to be the case.

An Associated Press reporter who went looking for Marzan in the Philippines in 2008 found his clinic abandoned, along with the adjacent family home in Moncada. Neighbors and village officials said the doctor's family had slipped out of town years ago and remained underground.

Marzan is the latest in the investigation to walk away without punishment.

Prosecutors last year dismissed indictments against a dozen other suspects, including Philippine doctors, spouses of military retirees and one Navy veteran, after agents failed to arrest them for years. The move came after Crabb ruled in one case that a lengthy pretrial delay violated a defendant's right to a speedy trial.

More than a dozen others have been convicted of defrauding the program. In the biggest case, a former health care company based in the Philippines was found guilty of submitting fraudulent and inflated claims to bilk the program out of $100 million.

Prosecutors say Marzan recruited dozens of military retirees and their dependents to falsely claim they received expensive services at his clinic so he could bill the program. The 35-count indictment, returned by a federal grand jury in 1999, said he submitted false claims of $1.5 million and was reimbursed for more than $1 million between 1990 and 1996.

The bogus claims covered a variety of medical services, such as hospitalization, radiology diagnosis and prescription drugs that were never delivered, according to the indictment. Prosecutors said Marzan would then give part of the claims he received back to retirees who participated in the scheme.

The claims were paid by Madison-based WPS Health Insurance, which has long held military contracts to process Tricare claims. That's why the investigation has been pursued by federal prosecutors in Madison.

Vaudreuil said Marzan could be the last pending Tricare fraud case in his office. He said he was "a little skeptical" the investigation had cut down the amount of fraud, but that administrative changes in the program may have a bigger impact.