KANSAS CITY, Mo. (AP) — Authorities say a welder accidentally started a fire that spread from a suburban Kansas City apartment complex that was under construction to nearly two dozen homes.

Overland Park Fire Marshal Mark Sweany said the fire started Monday when a welder ignited wooden building materials at the multimillion-dollar CityPlace development. The blaze leveled one large, four-story apartment building and heavily damaged a second. Intense heat and the burning debris that rained down also spread the fire into a nearby neighborhood.

Three firefighters were treated for minor injuries.

Overland Park Fire Chief Bryan Dehner says the building where the fire started was “vulnerable” because it was so early in the construction process that it lacked fire deterrents such as sprinklers.