Researchers from UC San Francisco have finally found some solid evidence that points to a potential cause of the widespread Colony Collapse Disorder that is affecting bees in the U.S. And no, it's not mobile phones.

According to the LA Times, a single-celled parasite called Nosema ceranae has been found in affected hives from across the country. This fungus was responsible for widespread loss of bee colonies in Europe and Asia and may be playing a crucial role in the disappearance of bees in the U.S.

The fungus was also found in some hives where bees had survived. Two other fungi and half a dozen viruses have also been found in the dead bees.

Researchers have cautioned though that the results are still "highly preliminary" and are from only a few hives found in Le Grand in Merced County. "We don't want to give anybody the impression that this thing has been solved," said UCSF biochemist Joe DeRisi. Entomologist Diana Cox-Foster of Pennsylvania State University echoed DeRisi's caution, noting that by itself, N. ceranae "is probably not the culprit ... but it may be one of the key players."

Bee researchers haven't ruled out other factors such as pesticide exposure and inadequate food resources following a drought. "There are lots of stresses that these bees are experiencing," said Cox-Foster, noting that a combination of these factors could be responsible.

If the N. ceranae is found to play a role in CCD, there is still some hope for the bees, which are used to pollinate a third of the country's agricultural crops. There is evidence that the antibiotic fumagillin, used mainly against a closely related parasite called Nosema apis which also affects bees, will also work on N. ceranae.