BRAINERD — An explosive boom shattered a quiet afternoon in Brainerd Sunday and cut power to parts of the city.

The blast, about 1:45 p.m. at the St. Joe’s substation along Washington Street, sent a flash of flame and a plume of black smoke into the air. The substation is next to D&D Plumbing on the south side of Washington Street.

Brainerd Public Utilities reported the force of the blast was so powerful it moved the switch, estimated at 8,000 pounds or more, off its concrete foundation. Oil was thrown into the air splattering the sand outside the chain-link fence surrounding the high-voltage area.

The boom was so loud it brought many people out onto the sidewalks outside their homes. Children playing outside in north Brainerd ran and yelled for their parents.

Lights flickered in west Brainerd in the Westgate Mall and went out altogether for parts of north and south Brainerd, turning one stoplight on Washington Street into a voluntary four-way stop.

A little after 3 p.m. many homes and affected businesses along Washington Street — from Hardee’s to the SuperAmerica on North Fourth Street — had power restored. But Brainerd Public Utilities reported power was still out in some segments and the biggest concern was an expected lengthy wait to restore power to Essentia Health-St. Joseph’s Medical Center in north Brainerd, which has generator backups.

Power was back on at the hospital before 5 p.m. but homes in south Brainerd remained without power. One resident in south Brainerd wondered how long they’d have to wait, noting they are dependent on electric heat.

Brainerd Public Utilities Superintendent Scott Magnuson said crews focused on restoring power to the hospital and were bringing in more help as they worked to get power back on for the Crow Wing County government complex, Brainerd High School and south Brainerd from Tamarack Street north to the substation.

Magnuson said after power was routed around the blown switch, a problem was discovered in the transformer, which crews were working to locate. Magnuson expected power to be restored to all residents before the end of the day. Power was restored to south Brainerd residents about 6 p.m.

RENEE RICHARDSON, senior reporter, may be reached at 855-5852 or renee.richardson@brainerddispatch.com. Follow on Twitter at www.twitter.com/Dispatchbizbuzz.