The Northwest Territories Power Corporation says a partially collapsed transmission tower was the cause of a blackout in the North Slave region on Sunday.

The downed tower was spotted by helicopter on Monday morning. It’s located at one of the most northerly parts of the transmission line, about 140 kilometres north of Yellowknife.  

“Just in the middle of nowhere,” says Ken Dies, the corporation’s system control manager.

Dies says the tower is basically two wooden poles with a beam in between. One of the poles snapped in the middle and buckled.   

He says crews are working to make sure it doesn't create more problems.   

“Right now they're coming up with a plan to shore up the poles on either side,” Dies says. “They don't want it to become a domino effect, where one after another starts to collapse.”

Next they'll come up with a plan to replace the broken pole.  

Dies says they don't know why the tower snapped. It could have been just been that too much frost and snow had built up on it.  

He says some of the towers are getting older, but are inspected at least once and sometimes twice a year.   

The blackout left thousands of people in the region without power for nearly three hours in -40 C.  

Even with the downed transmission line, hydroelectric power has been restored to the North Slave. Backup diesel generators at Jackfish Lake were temporarily used to power Yellowknife, Dettah and Bechhoko.