KELSO, Calif. -

Federal officials say illegally dumped domestic sheep may have spread pneumonia that's killed more than 100 bighorn sheep in Southern California's Mojave National Preserve.    

The Riverside Press-Enterprise says four domestic sheep carcasses and some sheep pellets were found last month about 20 miles away from the center of the bighorn outbreak.      

Linda Slater, a spokeswoman for the 1.6 million-acre preserve, says scientists suspect someone trucking sheep to alfalfa fields in Imperial Valley for grazing illegally dumped sick or dead sheep in the Mojave.      

Bighorns began dying this summer and more deaths are expected. The animals have no immunity to the disease carried by domestic herds.