Electrical surges at a huge new National Security Agency data centre have reportedly fried equipment, melted metal and caused fiery explosions, delaying its opening for a year.

Ten meltdowns over the past 13 months have caused hundreds of thousands of dollars' worth of damage to machinery and baffled investigators at the agency's data storage complex in Utah, the Wall Street Journal reported on Tuesday.

The surges have apparently prevented the NSA from using computers at its biggest data centre, a key element in its ability to store and process information from electronic snooping.

A spokesperson, Vanee Vines, suggested in a statement that the 247-acre site, which encompasses 1.2m sq ft of enclosed space, was getting back on track. “The failures that occurred during testing have been mitigated. A project of this magnitude requires stringent management, oversight, and testing, before the government accepts any building.”

However, the cause of eight of the 10 surges, known as arc fault failures, remain disputed, and investigators have not ruled out further meltdowns, which were compared to flashes of lightning inside a 2ft box.

The $1.7bn facility, two years in the making, was due to host supercomputers to store gargantuan quantities of data from emails, phone calls, Google searches and other sources.

Sited on an unused swath of the national guard base near Bluffdale, a town outside Salt Lake City, it comprises four 25,000 sq ft halls filled with servers and cables, plus an additional 900,000 sq ft of space for technical support and administration. It was due to open next month.

Construction passed largely unnoticed until Edward Snowden's revelations about NSA surveillance put his former employer under intense scrutiny.

Experts have disagreed on the centre's potential. Some said it will just store data; others envisaged a capacity to not just store but analyse and break codes, enabling technicians to potentially snoop on millions of Americans and foreigners for decades to come.

William Binney, a mathematician who worked at the NSA for almost 40 years and helped automate its worldwide eavesdropping, said Utah's computers could store data at the rate of 20 terabytes – the equivalent of the Library of Congress – per minute.

The NSA chose Bluffdale largely because of cheap electricity. The centre uses 65 megawatts to run computers and keep them cool, racking up more than $1m in costs per month. The first electrical surge was on August 2012. The most recent occurred last month.

The US army corps of engineers, which is overseeing construction of the facility, said the cause of the problems had been identified and that a contractor was now correcting it. The centre would be “completely reliable” before being handed over to the NSA, said Norbert Suter, the corps' chief of construction operations.

Other testimony cast doubt on that, saying 30 independent experts had conducted 160 tests over 50,000 hours, and still did not agree on what caused eight of the 10 surges, nor on ways to prevent future surges.

The Journal report, citing documents and interviews, said builders cut corners, back-up generators failed tests, a cooling system remained untested and some technicians questioned the adequacy of the electrical control system.

David Eskelson, a spokesman for Rocky Mountain Power and Pacific Corp, which supplies electricity to the centre, said it was not to blame. “Our engineers conducted detailed studies to confirm – with NSA’s concurrence – that Rocky Mountain Power’s system was not the source of any of the problems.”

KlingStubbins, an architectural firm which designed the electrical system, referred questions to the army corps of engineers.

Mark Reid, Bluffdale's city manager, had no information on the surges. “Any time you start a new building I know you always have problems. But I deal with water, not electricity. I have no idea what they're doing up there.”

The muddle underlined the NSA's expanding need for data centre management expertise, mixing electrical, computer and organisational skills. It has advised the University of Utah on a new data-management course which will offer internships at the Bluffdale facility.