Search and rescue teams took to the air in helicopters and the ground on foot on Sunday looking for anyone who might still be alive. Their spirits had been raised late Saturday night when they heard voices calling for help from the flotsam of trees, dirt and wreckage. Dangerous conditions forced them to turn back in the darkness, but they resumed their work at first light Sunday.

“We didn’t see or hear any signs of life out there today,” Snohomish County Fire District 21 Chief Travis Hots said. “It’s very disappointing to all emergency responders on scene.”

Snohomish County sheriff’s Lt. Rob Palmer said four more bodies were discovered late Sunday. Earlier in the day, authorities said one body had been found on the debris field. Three people were already confirmed dead on Saturday.

More people remained missing, and authorities said the number was “fluid.” Earlier Sunday, they said it was at least 18, but that count came before additional bodies were discovered.

The 1-square-mile slide also critically injured several people – including an infant – and destroyed about 30 homes.

Crews were able to get to the soupy, tree-strewn area that was 15-feet deep in places Sunday after geologists flew over in a helicopter and determined it was safe enough for emergency responders and technical rescue personnel to search for possible survivors, Hots said

He added that they did not search the entire debris field, only drier areas safe to traverse. Hots said crews were still in a “search and rescue mode. It has not gone to a recovery mode at this time.”

Searchers planned to continue looking through the night.

Before crews could get onto the debris field late Sunday morning, they looked for people by helicopter. They had late Saturday heard people yelling for help, but they were unable to reach anyone. The soupy mud was so thick and deep that searchers had to turn back.

“We have this huge square-mile mudflow that’s basically like quicksand,” Hots said Sunday.

The slide wiped through what neighbors described as a former fishing village of small homes — some nearly 100 years old.

As the search for the missing continued, authorities said some may have been able to get out on their own. The number unaccounted for could change because some people may have been in cars and on roads when the slide hit just before 11 a.m. Saturday.

Officials described the mudslide as “a big wall of mud and debris.” It blocked about a mile of State Route 530 near the town of Oso, about 55 miles north of Seattle. It was reported to be about 15 feet deep in some areas.

Authorities believe the slide was caused by ground made unstable by recent heavy rainfall.

Washington Gov. Jay Inslee described the scene as “a square mile of total devastation” after flying over the disaster area midday Sunday. He assured families that everything was being done to find their missing loved ones.

The slide blocked the North Fork of the Stillaguamish River. With the water pooling behind the debris, authorities worried about downstream flooding and issued an evacuation notice Saturday. The water had begun to seep through the blockage Sunday afternoon, alleviating some concerns.

Snohomish County officials said Sunday that residents could return home during daylight hours. Even though the evacuation had been lifted, Inslee urged residents to remain alert.

The National Weather Service issued a flash flood watch for Snohomish County through Monday afternoon.

Shari Ireton, a spokeswoman for the Snohomish County sheriff’s office, said Sunday that a total of eight people were injured in the slide.

A 6-month-old boy and an 81-year-old man remained in critical condition Sunday morning at Harborview Medical Center in Seattle. Hospital spokeswoman Susan Gregg said two men, ages 37 and 58, were in serious condition, while a 25-year-old woman was upgraded to satisfactory condition.

Bruce Blacker, who lives just west of the slide, doesn’t know the whereabouts of six neighbors.

“It’s a very close knit community,” Blacker said as he waited at an Arlington roadblock before troopers let him through.

Search-and-rescue help came from around the region, including the Washington State Patrol and the Army Corps of Engineers. More than 100 were at the scene.

Dane Williams, 30, who lives a few miles from the mudslide, spent Saturday night at a Red Cross shelter at the Arlington school.

He said he saw a few “pretty distraught” people at the shelter who didn’t know the fate of loved ones who live in the stricken area.

“It makes me want to cry,” Williams said.

Hots said searchers would continue their efforts through the difficult debris field.

“There may be people in their cars, there may be people in houses,” he said.