The cause of the collapse on Mersey St was not immediately apparent this afternoon, and was listed by PowerNet as "being investigated".
In an update this evening PowerNet chief executive Jason Franklin said it was thought a vehicle had hit one of the poles, which had fallen and dragged the two others down.
Earlier, employees at a nearby business said they heard a loud bang followed by a momentary loss of power.
They said a fellow employee was taking a break outside when they witnessed the power poles collapse one after the other "like dominoes".
PowerNet listed the outage as occurring at 3.15pm.
Affected localities included Bond St, Invercargill Inner City, and Mersey St.
No injuries or damages to property have been reported.
Mr Franklin said investigations were ongoing, and that power had been restored to most users by 8.30pm.
