The Clay fire, which broke out Tuesday in a river bottom in Riverside County east of Los Angeles, quickly spread to nearly 40 acres. But by Tuesday night, crews had stopped its progress and were doing “extensive mop-up operations,” Riverside officials said. It was 40 percent contained as of 4 a.m. Wednesday, according to Cal Fire.

Santa Ana winds will continue whipping through Southern California through Thursday, sparking fears that progress made fighting wildfires that have scorched over 40,000 acres and left 28 dead could be reversed and more blazes could break out.