Joe Incandela in a screenshot from the video on CERN's website.
A video mistakenly posted online appears to confirm that scientists have discovered the elusive Higgs boson particle.
According to a video that was briefly made public on the website of the European Organisation for Nuclear Research (CERN), the search for an answer to one of science's greatest mysteries may be over.
"We've observed a new particle ... we have quite strong evidence that there's something there," Joe Incandela, spokesman for the CMS experiment at CERN's Large Hadron Collider, says in the video.
"This is the most massive such particle that exists, if we confirm all of this - which I think we will."
After being available to the public for a brief period of time by mistake, the video now exists in a password-protected part of the website.
"It may in the end be one of the biggest discoveries, or observations, of any new phenomenon that we've had in our field in the last 30 or 40 years," Incandela says in the video.
"When we say we've observed a particle, it means we've just got enough data to say that it's definitely there and it's very unlikely to go away ... we then need more data to start to ascertain its characteristics, what are its properties."
The researchers are expected to announce the successful results tonight at a joint seminar in Geneva and Melbourne, where the International Conference on High Energy Physics is being held.
Commonly described as the last ingredient to the standard model of particle physics, scientists have been hunting the Higgs boson for almost 50 years.
It is often know as the "God particle" as it is thought to give all other particles in the universe their mass, and will help scientists understand how the universe was formed.
Research into the the mysterious particle has taken place at the $9.78 billion Large Hadron Collider, a giant atom smasher that was built underground on the Swiss-French border.
A spokeswoman for CERN confirmed that the video was not meant to have gone up online, and is one of several that was pre-produced to cover different possible results of the research.
"Even we in the press office do not know what they are going to announce," said Corinne Pralavorio.
with Deborah Smith