WIDGEE couple Brad and Jenny Sonter saw it happen and thousands of Gympie people heard the 11,000-volt explosion in Nash St on Tuesday.
The Sonters had driven through Mary St and had only seconds previously turned into Nash St when their vehicle's dash cam captured the moment.
Shops, restaurants and homes were suddenly plunged into darkness through much of the CBD and some surrounding areas, when a loud explosion on a Nash St power pole smashed an insulator to tiny pieces, throwing them across, up and down the street, even damaging parked cars.
The couple had just rounded the corner near the Zion Retirement Village when their conversation was suddenly halted by the sight of the sudden flash and the sound of the blast.
Southside residents, shopkeepers up Mary St and startled office workers heard the bang.
Damage spread quickly as the Nash St fault tripped circuit breakers at the Energex Pine St substation, affecting homes and businesses in Channon St and out to Gympie Hospital, Cartwright Rd, Pine St, Corella Rd, Duke St, Popes Rd and Cooinda St.
Traffic lights were quickly restored at the Duke and Channon Sts intersection, but others at the Monkland St intersections with Nash and Mary St remained out.
Police switched to emergency power at their Channon St station and headquarters and Gympie courthouse was all but out of action.
Two hearings were adjourned and staff had to write manual receipts when people came in to make payments over the counter.
Emergency repair crews said they were working to gradually restore power, firstly to "low voltage circuits," including some shops.
Gympie RSL Club was unable to serve lunches during the blackout, which lasted for about three hours from 9.18am.
A spokesman for Energex said the explosion was caused by a switch failure on equipment attached to the power pole, just outside The Gympie Times office.
That tripped out the sub station at Pine and Woodbine Sts.
Glass and ceramic debris blasted across the street was the remains of an insulator, he said.
Crews were quickly on the scene, urging pedestrians to keep clear for safety reasons as they pondered a big job ahead of them, wondering if it would even be repaired by the end of the day.
"They were on the scene quickly and worked to progressively restore power over the next three hours," the spokesman said.
He said it was often hard to determine the cause of dramatic equipment failures.
"It could be weather related, but even the effects of lightning strike do not necessarily happen immediately," he said.
"It could be weather related, if for example a lightning arrester is struck, but does not fail immediately.
"Then, days later sometimes, it could fail, even in good weather," the spokesman said.