Leroy Jackson made a lot of enemies battling logging and mining on the nation's biggest Indian reservation. And fellow environmentalists suspect he may have been murdered by one of them.

The Navajo activist was found dead Oct. 9 of what was ruled a methadone overdose. But his wife, his doctor and the people he worked with swear he was a fitness buff who never took drugs."We still believe there was foul play," said Lori Goodman, a close friend and spokeswoman for the environmental group he co-founded.

Police in New Mexico, where Jackson's body was found in his van along a remote highway, have not closed the books on the investigation.

Jackson, 47, of Tsaile, was found dead about 25 miles south of the Colorado state line. The curtains in the windows of the parked van were closed and a blanket covered the body. He had been reported missing eight days earlier.

Jackson was a founder of Dine Citizens Against Ruining the Environment, an environmental group on the Navajo reservation, which stretches across parts of Arizona, New Mexico and Utah.

Jackson and Dine CARE (Dine is the Navajo-language name for the tribe) sought to limit logging on the reservation to protect the Mexican spotted owl, a threatened species.

Before he disappeared, Jackson said he had obtained documents that showed Bureau of Indian Affairs officials were improperly trying to get the tribe exempted from the federal logging restrictions designed to protect the owl.

Sam Hitt of the Santa Fe., N.M.-based environmental group Forest Guardians said last week that Jackson also was planning to protest alleged corruption in the tribe's logging company, Navajo Forest Products Industries.

Many Navajos who argue that logging, mining and other such ventures are essential to fighting poverty and unemployment on the reservation were angered by Jackson's efforts. He once was hanged in effigy at a loggers' rally, and friends say he had received death threats.

Norman Birtcher, operations manager for Navajo Forest Products, denied the industry had anything to do with his death.

"That is preposterous," Birtcher said from the company's office in Navajo, N.M. "Leroy Jackson was respected, although we had different agendas. He was articulate and persistent."

Jackson's death certificate says he died of "methadone intoxication." Methadone is used to wean addicts from heroin. But final autopsy results have not been released, and it was not immediately known when they would become available.

The New Mexico State Police list the case as an "unattended death," which means no one was around when the body was found who could give any indication of what preceded the death.

Jackson's wife, Adella Begaye, was hesitant to discuss conspiracy theories but insisted her husband wouldn't knowingly have taken methadone.

"Leroy was a healthy man; he was not a drug addict," she said. "My husband didn't take heroin so I don't know how he could have taken methadone."

Jackson's physician and neighbor, Dr. David Lange, said Jackson did not use drugs.

Rep. Bill Richardson, D-N.M., has asked the FBI to investigate, citing "a strong possibility that a major crime was committed."