The world's largest particle collider will be down for at least two months following a helium leak into the tunnel, a spokesman for the European Organisation for Nuclear Research (CERN) said Saturday.

James Gillies told AFP: "There has been an incident in a test. One section of the machine will have to be repaired."

CERN said in a statement that a fault occurred on Friday afternoon, resulting in a "large helium leak into the tunnel.

"Preliminary investigations suggest that the most likely cause of the problem was a faulty electrical connection between two magnets, which probably melted at high current leading to mechanical failure," it said.

There was no risk to people, added the centre, saying that a full probe was underway.

As the sector where the fault occurred would have to be warmed up for repairs to take place, the Large Hadron Collider (LHC) was expected to be halted for "a minimum of two months."

The LHC was started on September 10, but it had to be shut down because of a fault in the cooling system.

It was turned back on again on Friday, but the latest incident has once again forced operations to halt.

The LHC took nearly 20 years to complete and at six billion Swiss francs (3.76 billion euros, 5.46 billion dollars) is one of the costliest and most complex scientific experiments ever attempted.

It aims to resolve some of the greatest questions surrounding fundamental matter, such as how particles acquire mass and how they were forged in the "Big Bang" that created the universe some 13.7 billion years ago.