VAN NUYS (CBSLA) — A vacant five-story commercial building fire that was believed to be extinguished on Sepulveda Boulevard flared up again Sunday night.

Fire crews worked to put out hot spots inside the building, hours after they declared a knock down. The structure had been abandoned for a number of years.

Earlier, LAFD Spokesman Brian Humprhey had said the “relentless teamwork” of 125 firefighters enabled them to extinguish the blaze in about an hour and 45 minutes. An Urban Search and Rescue crew searched the “structurally unsound” building and hadn’t discovered any victims.

Police assisted LAFD in moving a large contingent of homeless people congregating in tents in an adjacent parking lot to prevent them from being struck by falling debris.

Marcos Rodgriguez was working across the street from the blaze and says he noticed someone going into the building: “I don’t know if they were fighting or something like that, but then a few minutes later the fire started.”

Investigators aren’t sure if the homeless population is connected to the fire, but neighbors says encampments are often cleared out and they eventually return.

“We want the homeless to have a place, but obviously we want them to have a place that doesn’t impact us,” says local resident Lewis Hatkoff.

LAFD says crews will remain on site, and the closure of Sepulveda Boulevard between Vose and Sherman Way is expected to continue Sunday night.