Physicists have moved to quash rumours that the elusive Higgs boson - dubbed the God particle - has been detected by a US "atom smasher".
A spokesman for the lab which operated the Tevatron accelerator denied scientists had made a discovery there.
The Tevatron, based at Fermilab in Illinois, is the US rival to Europe's Large Hadron Collider (LHC).
The rumours were made public in a blog post by an Italian particle physicist.
But a spokesman for the Fermi National Accelerator Laboratory (Fermilab) told BBC News: "There is no merit to the rumours of a Higgs discovery."
On Tuesday, the laboratory's Twitter feed said: "Let's settle this: the rumours spread by one fame-seeking blogger are just rumours. That's it."
Stefan Soldner-Rembold, a spokesperson for the DZero experiment at the Tevatron, told BBC News: "There is no evidence yet of a Standard Model Higgs signal; more data will be needed for that.
"The rumours started by the blog are not correct and blogs are not a reliable source of information."
The Higgs boson is of huge importance to the widely accepted theory of physics, known as the Standard Model.
It is the sub-atomic particle which explains why all other particles have mass.
However, despite decades trying, no-one, so far, has detected it.
Last week, Tommaso Dorigo, who is a physicist at the University of Padua in Italy, wrote on his blog: "It reached my ear, from two different, possibly independent sources, that an experiment at the Tevatron is about to release some evidence of a light Higgs boson signal.
"Some say a three-sigma effect, others do not make explicit claims but talk of a unexpected result."
"Three-sigma" refers to the statistical certainty of the result - a 99.7% likelihood of an accurate measurement.
However, errors and fluctuations in the data mean that high energy physicists require an effect of five-sigma to produce convincing evidence of a discovery.
On Tuesday, physicist and blogger Lubos Motl published more detail on the Tevatron rumours. But he noted that the anonymous source for his information was sceptical of the observation.
Finding the Higgs is the primary aim of the £6bn ($10bn) Large Hadron Collider (LHC) experiment near Geneva. But the giant particle smasher is not expected to be capable of searching for the signal from a Higgs boson until 2011 at the earliest.
So the possibility remains that the Tevatron could still make a discovery before the European machine.
Particle physicists are set to present new data from their experiments at the International Conference on High Energy Physics (ICHEP) in Paris from 22-28 July.