NAPA, Calif. — With roads still blocked by the police and fires still raging across broad swaths of Northern California, Matt Lenzi hiked through smoke-choked vineyards and waded the Napa River to reach the home his father lived in for 53 years. In its place, he found only blackened debris, blackened earth, and ash.

“Every piece of vegetation was gone,” said Mr. Lenzi on Tuesday, after going back in the vain hope of finding the pet cat that his father, Carl Lenzi, who is in his 80s, left behind when he fled for his life. “Even the barbecue melted, and that’s built to take heat.”

The fires ravaging California’s wine country since Sunday night — part of an outbreak of blazes stretching almost the entire length of the state — continued to burn out of control on Wednesday, as the toll rose to at least 21 people confirmed dead, hundreds hospitalized, and thousands of buildings destroyed or damaged. But state and local officials warned that with several hundred people still missing and unaccounted for, and some areas still out of reach of emergency crews, those figures are almost certain to rise.

The two biggest and most destructive fires had consumed more than 70,000 acres in Napa and Sonoma Counties by Wednesday morning, up from 52,000 on Tuesday afternoon, according to Cal Fire, the state’s firefighting agency. In all, six fires had burned more than 91,000 acres in the two counties, and Cal Fire rated all but the smallest of them as 3 percent contained, or less.