Kentucky State Police say the preliminary cause of death for a census worker found near an Eastern Kentucky cemetery is asphyxiation.

The body of 51-year-old William E. Sparkman was found in rural Clay County on September 12, 2009.

State Police said in a statement Thursday, Sparkman was found with a rope around his neck that was tied to a tree but his body was in contact with the ground.

"Well, this investigation, of course, is a death investigation, I want to reiterate that. We have not ruled out any one of the possibilities that would be resulting in a person's death," says Trooper Don Trosper, Kentucky State Police.

The Census Bureau has suspended door-to-door interviews in the area until the investigation is complete.

The federal government says Census employees are trained to deal with angry or hostile people.

They're advised to listen respectfully, empathize, and remain calm and detached.

Census Bureau safety records show there have been 21 work related deaths involving census employees in the last 11 years.

Most of them involved automobile deaths.