The rather charred remains of the balloon that caused the power outage on the North Coast on the Fourth of July in 2015.

SEASIDE — A power outage that disrupted holiday celebrations and affected more than 8,000 customers was caused by a metallic-skinned helium balloon that got away, according to Pacific Power.

Seaside, Gearhart and parts of Warrenton were without power from about 4:40 to 10:20 p.m. as Pacific Power crews replaced the damaged equipment.

“We found unmistakable red, white and blue Mylar shreds when we did the repairs the evening of July 4,” said Steve McGrorty, Pacific Power’s operations manager for the North Coast.

The balloon from a nearby celebration caused a main substation transformer to short circuit near Seaside Factory Outlet Center. Other equipment was also damaged on nearby poles.

“Balloons may seem like small things,” Pacific Power Safety Manager Gene Morris said. “But when escaped balloons touch power lines or substations, even the smallest amount of metal content material can conduct electricity. This can interfere with lines, causing power fluctuations and outages.”

When a balloon “gets in there in the wrong spot, it just basically short circuits the transmitting of the electricity,” added Pacific Power spokesman Tom Gauntt.

As soon as the power went out, the Seaside Fire Department called the substation to respond to the incident. The failed transformer had smoke coming from it, but flames were not detected, Seaside Division Chief Chris Dugan said. There was not much for the fire department to do, he said, but they were told it would be a significant outage.

The second transformer at the substation that can provide backup was going through regular maintenance and was not usable at the time, Gauntt said.

Local Pacific Power employees were the first to respond when the outage occurred. They “went to work on finishing the maintenance on the second transformer so that it would be ready to use when the Portland crew arrived,” Gauntt said.

The crew from Portland specializes in installing transformers and other equipment in substations.

“Both special and local crews were involved in the delicate switching work entailed with bringing the newly installed transformer back on line,” Gauntt said.