(CNN) - Search and rescue crews found the body of a 25-year-old woman Saturday morning, raising the death toll from the California mudslides to 19, authorities said.
The body of Morgan Corey of Montecito was found in mud and debris, Santa Barbara County Sheriff Bill Brown said. Her 12-year-old sister, Sawyer, was found dead earlier this week.
Five people are now missing, the sheriff said, and searchers continue to go through damaged and destroyed homes.
Emergency workers on the ground have doubled since Thursday, with about 1,250 trying to find and rescue those still trapped, Santa Barbara County spokeswoman Amber Anderson said.
The mudslides, which came in the early morning hours of Tuesday, destroyed dozens of homes. Those killed ranged in age from 3 to 89, and all lived in Montecito in Santa Barbara County, northwest of Los Angeles, authorities said.
Rescuers have searched frantically for the missing after rivers of mud and boulders flooded through neighborhoods in and near Montecito, an affluent seaside community east of Santa Barbara, demolishing homes and leaving roads impassable.
"In disaster circumstances, there have been many miraculous stories of people lasting many days. We certainly are searching for a miracle right now," Brown said Thursday.
"But realistically we suspect that we are going to continue to have discovery of people who were killed in this incident."
How to help the victims of the California mudslides
Evacuation zone increased
The immediate areas where people were killed are under mandatory evacuation, and officials increased the size of the evacuation zone Thursday.
"We know that this a terribly inconvenient development, but it is also incredibly necessary," Brown said.
"This entire area is a very active rescue and recovery and repair zone right now," he said.
He said the zone, which includes areas formerly under voluntary evacuation advisories, would be in effect for one week but that residents should plan for two.
Rescue workers are using helicopters and all-terrain vehicles in a search hampered by blocked roads and downed trees and power lines.
Billy Grokenberger lives in a part of Montecito that was under a voluntary evacuation order. He and his parents put belongings in three cars in case they decided to leave before the storm. They didn't.
"We had thought about leaving, but we had just had the fires," he said, referring to the recent wildfires that stripped the area of needed vegetation. "... We didn't take it serious(ly) enough."
On the morning of the storm, Grokenberger watched as 2 to 3 feet of water streamed down the street.
"(In) four minutes the water was through our wall and in our house, almost to the second story," he said.
"The house is destroyed, but you know, there's just so many others who are less fortunate. But we just feel lucky that we were able to get out and (are) alive."
Risk of mudslides for years
The storm hit hard between 3 and 6 a.m. Tuesday. The rain poured down on hillsides charred by recent wildfires, which burned vegetation that otherwise could make the terrain more resistant to mudslides.
The Thomas Fire -- the largest wildfire in California's recorded history -- burned more than 281,000 acres in Santa Barbara and Ventura counties from early December into this month. It wasn't fully contained until this week.
Geologists and forecasters warned that intense rain could trigger deadly mudslides from the scorched areas.
And because of the fire, communities below the scarred terrain could remain at risk of mudslides for years, said Randall Jibson, a research geologist with the US Geological Survey.
Montecito may be at slightly less risk now, because this week's flooding already brought down vulnerable material.
"(But) no storm brings down everything that is susceptible. There's almost always more" that could come down, Jibson said.
What can be done? Long term, one option would be more basins to slow down storm runoff and collect debris.
Short term, making the public ready to evacuate during heavy rains is key, he said.
Montecito and Carpinteria are especially vulnerable to mudslides because the steep terrain in some places goes from thousands of feet above sea level to sea level in just a few miles, said Tom Fayram, a deputy public works director with Santa Barbara County.