Wichita ? Three whitetail deer killed by hunters in northwest Kansas have tested positive for chronic wasting disease, wildlife officials said.

Now officials are trying to find the source of the disease, which could have come naturally from Nebraska or been spread to wild deer from a captive herd of deer or elk.

It is the third time the disease has been found in Kansas.

It first appeared in a Harper County captive elk imported from Colorado in 2001, according to Mike Miller, a spokesman for the Kansas Department of Wildlife and Parks. In 2005, a whitetail doe from Cheyenne County, also in northwest Kansas, tested positive for the disease.

About 3,000 deer were tested after the 2006 hunting season with no sign of the disease.

The three deer that tested positive for the disease after the 2007 season were killed in the northern part of Decatur County along Sappa Creek, according to the Department of Wildlife and Parks.

Also, Nebraska biologists found two other deer with the disease within a few miles of the Kansas border north of Decatur County, Miller said.

The disease is often passed from deer to deer and has been known to remain in the soil for several years.

Chronic wasting disease – a close relative of mad cow disease – is untreatable and always fatal to infected deer, elk and moose, but it is not believed to be transmitted from deer to people or livestock. While officials recommend against eating meat infected with the disease, the Department of Wildlife and Parks says people should not be afraid to consume Kansas venison.

Some people worry the disease could lead to fewer deer, possibly hurting the state’s multimillion-dollar deer-hunting industry.

Kansas has been testing for the disease for about 10 years, taking samples from deer volunteered by hunters.

Miller said the department is testing about 2,200 samples this year and about one-third have been checked so far.