GUATEMALA CITY -- An American hotelier and farmer who was murdered under mysterious circumstances in northern Guatemala this spring has become a focus of contention between the U.S. and Guatemalan governments.

Michael V. DeVine, 49, a native of Belleville, Ill., was beaten and decapitated in June near the farm and inn he had run with his wife since 1970 in Peten, a remote timber-growing area near Guatemala's eastern border with Belize.

Six Guatemalans -- five Army soldiers and a civilian -- have been arrested and charged in the case, and President Vinicio Cerezo has said that "people linked to the {government's} security forces could be responsible for the death."

But diplomats and others close to the investigation say that only some of those in custody were probably involved in the murder, and that others who were probably involved have not been apprehended.

Among envoys and others close to the investigation, there is a growing feeling that Guatemalan military authorities, who are in charge of both investigating and trying the case, have not produced any leads and are dragging their feet on the case.

"I personally feel they know perfectly well who was involved and they are not coming forward," said one envoy.

Among the concerns is that the military officer in charge of the military forces in Peten at the time DeVine was killed, Col. Mario Roberto Garcia Catalan, has not been officially questioned in the course of the investigation. He was withdrawn from the post this fall and replaced by another colonel, who has promised to resolve the case.

Nor has there been official questioning of the regional head of military intelligence, known in Guatemala as G-2. A source close to the case said that most of those arrested so far worked with G-2, which for years has been notorious in Guatemala for intimidating, abducting and murdering leftist guerrillas, their supporters and others who annoy the army.

Diplomatic sources said that U.S. Ambassador Thomas Stroock, who has shifted American policy here by pressing the Guatemalan government on human rights issues, raises the DeVine case frequently with Cerezo and top military officers. Stroock was recalled for consultations by the State Department in March in a protest over continuing human rights abuses.

In a letter to Stroock dated Sept. 6, Cerezo pledged to pursue the DeVine investigation and "apply the sanctions the law establishes."

However, promises in the past by Guatemalan authorities to prosecute human rights cases have generally not amounted to much, particularly when military involvement is suspected.

The Guatemalan military, which ruled the country through a succession of dictatorships until 1986, remains largely autonomous, and no officer has ever been prosecuted or convicted for a human rights violation. The impunity has extended to cases involving Americans.

In 1985, for example, two Americans were killed in the Guatemalan highlands near a guerrilla zone. Their bodies were never found, but villagers later told the U.S. Embassy that they had been shot by five civil patrolmen. Civil patrols are organized and overseen by the army.

While some diplomats say they are hopeful that those responsible for killing Devine will be prosecuted and convicted, others close to the investigation are not so confident.

The only reason the case has progressed as far as it has, they note, is that DeVine's widow, Carole, has hired an American private investigator.

No one is certain what motive there was for the murder, although theories abound. Some say that Devine, who was a guide for tourists wanting to explore the Peten wilderness, may have unwittingly stumbled across an illegal timber or drug enterprise. Others believe he may have been the victim of a contract killing arranged by a soldier thrown out of his restaurant for rowdiness several years ago. He even may have been the victim of a case of mistaken identity.

Most agree the murder was probably not planned by high-ranking officers. Despite widespread human rights abuses by the military in Guatemala, soldiers tend to stay clear of Americans.

DeVine was a well-liked and successful farmer and businessman, described by those who knew him as hard-working and upstanding, even a little square.

Shortly before his death, DeVine became morose and hinted to some of his employees that he had received a death threat, a source close to the investigation said.