Dark matter --- the elusive component that scientists say makes upwards of 85 percent of the universe --- may have been spotted in an experiment far below the surface of the Earth.
The new results come from the Super Cryogenic Dark Matter Search, which takes place deep within northern Minnesota's Soudan mine, reports Space.com.
Dark matter emits no light but interacts with the universe through its gravity, scientists believe.
Researchers in the subterranean laboratory chill germanium and silicon to very cold temperatures --- to absolute zero, which is minus 459.67 degrees Fahrenheit and minus 273.15 degrees Celsius --- in hopes of detecting dark matter as it intersects with a frigid atom, which results in an electrical charge and release of heat. The reaction would be measured with ultra-sensitive instruments.
And, in fact, the experiment observed three events could have resulted from a weak dark matter particle passing through.
The detected events, however, could have also been simply statistical hiccups. The research team noted they would expect to see similar readings about 5 percent of the time, thanks to random fluctuations.
But the events recorded by the experiment happened within a similar energy range, which was less likely to have been random.
Blas Cabrera, a Stanford University physicist, said the observations were 99.81 percent more likely to be indications of a weak dark matter particle than background fluctuations.
The finding "does not rise anywhere near the level of discovery, nor does it rise anywhere near what we would call 'evidence,' Cabrera said. It is, however, a "region of interest" for future study.
"We're not claiming anything," he said.
If the signals turn out to be evidence of dark matter, they suggest a particle with a mass of about 8 giga-electronvolts, or GeVs, where one GeV equals 1 billion electron volts.
That mass would be consistent with earlier Super CDMS results and those of another dark-matter-hunting experiment staged by the U.S. Department of Energy's Pacific Northwest National Laboratory.
On the other hand, Cabrera said, the new findings seem to contradict results produced by the international XENON Dark Matter Project, a major experiment located in Italy.
Earlier this month, NASA scientists announced that they'd seen hints of dark matter from indirect measurements taken on the International Space Station.
The detector, the Alpha Magnetic Spectrometer, detected 400,000 positrons, which are the antimatter equivalent of electrons in the known world of matter.