Scientists are becoming more confident that they will be able to contradict Einstein's assertion that nothing can travel faster than light, after carrying out another test.
Italian physicists first made the startling claim in September but have now repeated an adapted version of their experiment, which produced the same result.
The test suggests that sub-atomic particles called neutrinos can break the barrier.
If such tests can be repeated, they would challenge one of the fundamental assumptions of modern physics.
Scientists yesterday submitted their latest findings to the Journal of High Energy Physics for consideration.
They said that they had waited until now to submit the paper to take into account suggestions from other scientists and carry out a new test.
They beamed neutrinos through 730 kilometres (454 miles) of rock from the nuclear research facility Cern in Switzerland to Gran Sasso, Italy.
A light beam would take 2.4 milliseconds to travel the distance - but both experiments have shown a neutrino can beat it there by 60 billionths of a second.
In 1905, Albert Einstein stated in his theory of special relativity that nothing can travel faster than a light beam in a vacuum - 168,282 miles per second.
According to the theory, it would take an infinite amount of energy to exceed light speed.
The tests were carried out by Opera - the Oscillation Project with Emulsion Tracking Apparatus.
Fernando Ferroni, president of the Italian Institute for Nuclear Physics, said: "A measurement so delicate and carrying a profound implication on physics requires an extraordinary level of scrutiny.
"The experiment Opera, thanks to a specially adapted Cern beam, has made an important test of consistency of its result.
"The positive outcome of the test makes us more confident in the result, although a final word can only be said by analogous measurements performed elsewhere in the world."
Physicists in Japan will now try to repeat the experiment, with the help of scientists from Liverpool University.
Professor Themis Bowcock, head of the university's particle physics team, said: "Should neutrinos travel faster than light, it would overthrow our ideas of the structure of space and time.
"Physicists are therefore treating the results of the experiment with caution and looking to test them again through our separate experiments to be certain of what these results are telling us.
"The University of Liverpool team is working in Japan, which can measure neutrino velocities over a slightly shorter distance (230km) from Tokai to Kamiokande on the T2K (Tokai to Kamiokande) experiment."