The "positive outcome of the [second] test makes us more confident in the result," Fernando Ferroni, president of the Italian Institute for Nuclear Physics, said in a statement late Thursday.
Ferroni is one of 160 physicists involved in the international collaboration that performed the experiment known as Opera -- Oscillation Project with Emulsion-tRacking Apparatus.
A large number of skeptical physicists suspected the original measurements done in September were in error, The Washington Post reported.
The Opera team said in running an improved experiment 20 times, they found almost exactly the same result.
"This is reinforcing the previous finding and ruling out some possible systematic errors which could have in principle been affecting it," Antonio Ereditato of the team said.
"We didn't think they were, and now we have the proof," he told BBC News. "This is reassuring that it's not the end of the story."
Although the repeat experiment "has made an important test of consistency of its result," Ferroni said, "a final word can only be said by analogous measurements performed elsewhere in the world."
For more than 100 years, the speed of light has been assumed to be the universe's ultimate speed limit, and if the new experimental results are confirmed, the find could undermine one of the basic principles of modern physics.