MOUNTAIN VIEW, CALIFORNIA -- More than a dozen candidate signals have been snagged by a global network of volunteers in a search for extraterrestrial intelligence called SETI@home. But one by one, the prospective SETI hits have been downgraded to misses and tagged as radio interference.

The SETI@home project has been under way since May 1999. Using data collected by the worlds largest radio telescope in Arecibo, Puerto Rico, some 3 million volunteers around the globe have attempted to tease out from the telescopes star sweeping any signs of radio chatter eking from distant, inhabited worlds.

SETI@home is separate from the SETI Institute, which is engaged in several scientific and educational projects designed to search for extraterrestrial intelligence in the Universe. SPACE.com has a partnership with the SETI Institute.

In combing through the data, analysts eliminate signals that are caused by radio frequency interference, computer errors, and to keep an eye out for signals that repeat.

The result of that weeding through of data produced 17 extraterrestrial candidate signals -- those that show a pattern indicative of intelligence in the natural buzz and crackle of deep space.

"The most interesting signals are things that weve seen two or more times. We actually have a human being looking at the data, trying to figure our what are these repeating signals and why do we see them again," Werthimer said.

So far, however, all the candidate signals have turned out to be radio frequency interference. The patterns were found to be associated with the same radio frequency.

 "We know they are radio pollution because when the telescope is pointed to other places, we see them as well," Werthimer said. "The pollution is coming in from the side of the telescope."