SALT LAKE CITY (ABC4) — Rocky Mountain Power said electricity was restored Tuesday evening to most customers following a massive outage that affected roughly 15,000 customers for more than an hour.

The outage occurred around 5:30 p.m., shutting off power in and around the communities of Riverton, South Jordan and Draper.

A Rocky Mountain Power spokesperson said the outage appears to have been caused by an insulator malfunction by a piece of privately owned equipment. The malfunction, which happened at a substation, tripped the safety mechanism, cutting off power to thousands in the Salt Lake Valley.

The outage caused a traffic nightmare in the area. Images sent to ABC4 showed businesses — from gas stations to restaurants — sitting empty, with all their lights off.

Shortly after 7 p.m., crews restored power to the area.