Scientists hunting an invisible form of matter that pervades the universe and holds galaxies together claim to have found it underneath a mountain in Italy.

The discovery, at a laboratory built deep into the Gran Sasso mountain in Abruzzo, could end a 70-year race to find the elusive "dark matter" that physicists believe accounts for 90% of the mass of the universe. Its existence was first postulated in 1933 by a Swiss astronomer who observed that distant galaxies must be held together by a huge gravitational pull caused by some apparently invisible form of matter. It gained the name "dark matter" because it does not shine or reflect light.

Researchers led by Dr Rita Bernabei at the University of Rome claim that a giant detector inside the mountain laboratory has picked up signs of dark matter. The signal suggests that it could be made of theoretical particles known as axions. The discovery was announced at a physics conference in Venice. The experiment was designed to detect dark matter in space as Earth flies through it.

Scientists are unlikely to take this single result as hard proof. Many say the discovery will have to be replicated by groups around the world before they can be sure they have finally shed light on dark matter. Earlier this year British researchers became the latest to join the hunt, using a laboratory deep inside an old salt mine in Yorkshire. The labs are built underground to shield them from other particles that could smother dark matter signals.

"We are pretty sure now that this is not a statistical fluke," said astrophysicist Frank Halzen, of the University of Wisconsin-Madison, who heard Bernabei's talk at the conference. "We should pay attention to this. We should not just ignore it," he told New Scientist.