Power surges at the giant Utah centre had ruined equipment costing almost a million dollars.

The technical problems had also led to lengthy investigations that had meant its opening date had been pushed back.

The Utah plant is one of three the NSA is building to boost its data gathering and surveillance capabilities.

Over the past 13 months, 10 separate electrical surges have occurred at the data centre in Bluffdale, Utah, according to the Wall Street Journal (WSJ), which is reported to have cost $1.4bn (£872m) to build.

Each surge had burnt out and wrecked about $100,000 worth of computers and other equipment, it said.

The Bluffdale facility is more than one million sq ft (93,000 sq m) in size and its power costs are expected to top $1m (£622,000) a month, according to the WSJ.

The NSA had been supposed to start using the data storage and analysis centre in October 2012, it said, but this had been delayed by the damage caused by the power surges and a six-month investigation into their cause.

WSJ said civil contractors were confident the problem had been solved but a special US Army engineer investigation team had said the cause was "not yet sufficiently understood" to be sure that it would not happen again.

The amount of surveillance that the NSA carries out has come under scrutiny in recent months thanks to whistleblower Edward Snowden.

He leaked documents allegedly detailing its activities including the Prism programme that garners data from web firms including Google, Facebook, Microsoft and Yahoo.

In addition, the NSA has been found to be gathering data on phone calls made by US citizens.