The Large Hadron Collider (LHC) is recovering from a general power cut which affected the machine's systems.
Cern, the organisation operating the LHC, said it had taken until Monday morning for the machine to recover.
Power was cut to the entire accelerator complex at Cern, including the LHC, according to a spokesperson.
The outage after 2300 local time on Friday was probably caused by storms, but proton beams should be back in the machine by Wednesday.
The collider is currently in a technical stop to allow technicians access into the 27km-long tunnel housing the giant machine.
A spokesperson said a technical stop had already been scheduled for this week.
Dr James Gillies, director of communications at Cern (the European Organization for Nuclear Research) in Geneva, told BBC News: "It was all up and running again over the weekend."
He added: "The LHC is back in the state it was before it happened. We will have beam back in it on Wednesday."
The £6bn ($10bn) collider is being used to smash together beams of proton particles to shed light on the nature of Universe.
Over the past few months, engineers have been building up the intensity of the LHC's particle beams.
Physicists have said that if things continue to plan, the collider could soon probe a new mass range where novel sub-atomic particles are thought to exist.
A spokesperson stressed that power cuts occur periodically.
A previous outage in November 2009 which halted the machine is thought to have occurred when a bird dropped a baguette it was eating at one of the points where the mains electricity supply enters the collider from above ground.