The Large Hadron Collider, the world's largest atom-smasher, resumed operations on Sunday after being shut down and upgraded over the past two years.

In a communique, the European Organization for Nuclear Research, or CERN, said that it fired two beams of protons through the huge device and its 27-kilometer (16.8-mile) tunnel beneath the Swiss-French border near Geneva.

On March 24, CERN announced that the $150 million upgrade to the particle accelerator was complete but said that there would be a slight delay before protons could again be shot through it and high-energy physics experiments carried out because of an intermittent short-circuit.

CERN officials said, however, that the problem was a minor one and that it would have a minimal impact on the LHC's operations.

On Sunday, tests were carried out and more will be undertaken in the coming days to be sure that the device is working correctly, and - when that is verified - the energy flowing through the LHC will be gradually increased.

The device fires two beams of protons directly at one another and when the minute subatomic particles - one of the basic components of matter - collide, they do so with a combined energy of 13 teravolts.

During the coming new phase of operations, between 2016 and 2018, the upgraded accelerator will be able to utilize its full capacity so that researchers - hopefully - can shed light on the composition of so-called "dark matter," which, along with "dark energy," makes up most of the universe, but which has never been directly detected and about which little is known.

The LHC is the most powerful machine in existence, with hundreds of huge magnets that function like batteries, and the energy it uses when it fires proton beams into each other is equivalent to that required for an aircraft carrier to sail at 43 km (27 mi.) per hour or a passenger jet to fly at 700 km (435 mi.) per hour.

The tunnel is in the shape of a subterranean ring 27 km (16.7 mi.) in circumference and for the LHC to work properly, it must be cooled to -217 C (-359 F), lower than the temperature in outer space.

In 2012, researchers using the LHC made one of the most significant scientific discoveries ever when they detected - for the first time - the Higgs boson, a subatomic particle that had been predicted to exist by the Standard Model of particle physics. EFE