Investigators probing the death of a U.S. census worker found hanging from a tree with the word "fed" scrawled on his chest increasingly doubt he was killed because of his government job and are pursuing the possibility he committed suicide, law enforcement officials told The Associated Press.

"Fed" is American shorthand for U.S. government worker.

Two officials, speaking on condition of anonymity because they were not authorized to discuss the case, said no final conclusions have been made in the case. In recent weeks, however, investigators have grown more skeptical that 51-year-old Bill Sparkman died at the hands of someone angry at the federal government.

The officials said investigators continue to look closely at suicide as a possible cause of Sparkman's death for a number of reasons. There were no defensive wounds on Sparkman's body, and while his hands were bound with duct-tape, they were still somewhat mobile, suggesting he could have manipulated the rope, the officials said.

Sparkman's naked body was found Sept. 12 hanging from a tree yet in contact with the ground in a remote patch of the Daniel Boone National Forest in the state of Kentucky.

The strange case attracted national attention when it first came to light, prompting worries that it may be a sign of increased anger toward the federal government in the first year of Barack Obama's presidency.

Authorities say Sparkman died of asphyxiation where his body was found.

A spokesman for the FBI's Louisville, Kentucky field office declined to discuss any aspects of the case.

Capt. Lisa M. Rudzinski, commander of a state police post involved in the case, declined to confirm that there was any new focus in the probe.

"The Kentucky State Police are continuing to investigate the death of William Sparkman and have yet to determine whether it is homicide, suicide or accidental," Rudzinski said. "The investigation is continuing."

If officials do determine Sparkman did not die because of his government work, that would likely mean a less prominent role for the FBI in the investigation, assisting the Kentucky authorities but not preparing to bring a case to federal court.

Sparkman's adopted son has been adamant the case is murder.