DULUTH — A fire at Central Hillside medical equipment business sent smoke billowing across the neighborhood late Wednesday afternoon.

The Duluth Fire Department reported to Lake Superior Medical Equipment, 522 E. Fourth St., where a fire engulfed one of the business' vans and a stairway on the back side of the building. Firefighters were on the roof of the building and firefighters on the ground were spraying water on the back of the building as of 6:30 p.m.

In a release from the department late on Wednesday, firefighters reported wind created challenging conditions and led to the use of a Superior Fire Department ladder truck. The 148th Fighter Wing provided an air trailer to help the DFD refill air canisters.

Fire Chief Shawn Krizaj said around 6:15 p.m. the department did not know how or where the fire started, but it was likely burning in the medical supply store's lower unit. A civilian helped evacuate the four apartments above the store, he said.

"We haven't done any investigation, of course, yet," Krizaj said. "Right now we're still just trying to control the fire."

As of 8:35 p.m., fire had not spread to adjacent buildings, which share walls with the burning building.

Gas and electricity were cut off to the block during the firefighting effort.

News Tribune reporters on the scene heard explosions or "pops" and a "loud boom" coming from inside the building.

The business provides oxygen concentrators, among other products.

A rally of approximately 500 striking Essentia nurses and their supporters was gathered in the parking lot behind the business and down the alley — near the Ronald McDonald House — when smoke came over the crowd.

Krizaj said someone at the rally smelled smoke and called 911.

Much of the rally moved to St. Luke's, as scheduled.

This story has been updated several times, most recently at 10:26 p.m. on Sept. 14, to include information from a Duluth Fire Department release. It was originally posted at 6:07 p.m.