A spokeswoman from the US Department of Energy's Fermi National Accelerator Laboratory, which operates the powerful particle accelerator Tevatron, said the results would be released at 2100 GMT but offered no further details.
"Nobody knows what this is," said Christopher Hill, a theorist at Fermilab who was not part of the team, according to the New York Times.
"If it is real, it would be the most significant discovery in physics in half a century."
The Times report said the findings relate to a "suspicious bump" in the physicists' data and could involve "a new and unexpected version of the long-sought Higgs-boson."
Sometimes called the "God Particle," the Higgs-boson has long eluded physicists who believe it could explain why particles have mass and its discovery is one of the most sought-after in all of physics.