RENO (AP) - Researchers continue to look at tungsten in their study of a mysterious childhood leukemia cluster in Fallon.

ientists who gathered Friday at a University of Nevada, Reno symposium discussed the latest research into the Fallon epidemic and theorized the cluster might have been fueled by environmental factors that harmed the genes of the children.

Since 1997, 17 children with ties to Fallon have been diagnosed with acute lymphocytic leukemia. Three have died. Health officials say about one leukemia case in five years would be expected. The last child in the group was diagnosed in 2004.

Dr. Paul Sheppard, an Arizona tree-ring scientist, says his most recent study showed high levels of tungsten, compared with other metals, on tree leaves in Fallon.

But Sheppard says biomedical research is needed to determine whether there's a link between tungsten and the cancer cluster.

Dr. Mark Witten, a toxicologist at the University of Arizona, presented preliminary results of a study that indicates tungsten-laced water caused sterility in older male mice.

(Copyright 2008 by The Associated Press. All Rights Reserved.)

AP-NY-10-11-08 1959EDT