Scientists chasing the elusive particle known as the Higgs boson -- thought to be the origin of mass -- expressed disappointment when a U.S. lab turned up zip.

Scientists with the Tevatron particle accelerator at Fermilab in Batavia, Ill., near Chicago, released the results of a months-long effort to confirm the existence of the so-called "God particle," Fox News reported Friday.

"We do not see the signal," Dmitri Denisov, staff scientist at Fermilab, told the news network. "If it existed, we would see it. But when we look at our data, we basically see nothing."

"At this point I'd say the chances are 50-50 for the Higgs to exist at all," Denisov said.

The results -- submitted Friday to the science journal Physical Review Letters -- represent a setback for scientists who have been following the quest for the particle.

Contacted by Fox News in Geneva, Switzerland, a spokesman for European Organization for Nuclear Research -- which operates the Large Hadron Collider atom smasher -- said it was too soon for the lab to release any analysis, but something could be released in a few weeks.

"Still too early to get excited, I'm afraid," spokesman James Gilies said. "I think this story will reach a conclusion at the main summer conferences this year -- end of July. By then, the LHC [Large Hadron Collider] experiments will have analyzed enough data to be able to say something."