PARADISE, Calif. (CBSNews) -- The search for remains of victims of the devastating Northern California wildfire has taken on new urgency due to rain in the forecast for midweek that could complicate those efforts and bring significant winds with it.

The rain could also trigger mudslides and rockslides in areas of Southern California hit by wildfires, reports CBS Los Angeles.

At the same time, the rain could help douse flames and bring relief to firefighters on the front lines.

Up to 400 people fanned out Sunday to search the ash and rubble where homes stood before flames roared through the Sierra foothills town of Paradise and surrounding communities, killing at least 77 people in the deadliest U.S. wildfire in a century.

The death count only grew by one Sunday and firefighters managed to expand containment to 65 percent of the 234 square mile burn zone.

About 1,000 names remain on a list of people unaccounted for more than a week after the fire began in Butte County about 140 miles north of San Francisco, authorities said.

Authorities don't believe all on the list are actually missing and the roster dropped by 300 on Sunday as more people were located or got in touch to say they weren't missing.

The National Weather Service said rain in the forecast for the Paradise area could bring 20 mph sustained winds and 40 mph gusts, which could make it hard for crews to keep making progress against the blaze.

Wearing white coveralls, hard hats and masks, teams of volunteers and search and rescue crews poked through the smoky debris for fragments of bone before rains could wash them away or turn loose, dry ash into a thick paste. The so-called Camp Fire has destroyed more than 10,500 homes.

A team of 10 volunteers, accompanied by a cadaver dog, went from house to house in the charred landscape. They scrutinized the rubble in five-minute sweeps, using sticks to move aside debris and focus on vehicles, bathtubs and what was left of mattresses.

When no remains were found, they spray-painted a large, orange "0'' near the house and moved on.

Sheriff Kory Honea said it was within the "realm of possibility" that officials would never know the exact death toll from the blaze. He also questioned whether the search for remains could be completed by midweek when rain is forecast.

On Sunday afternoon, more than 50 people gathered at a memorial for the victims at First Christian Church in Chico, where a banner on the altar read, "We will rise from the ashes."

People hugged and shed tears as Pastor Jesse Kearns recited a prayer for first firefighters, rescuers and search teams: "We ask for continued strength as they are growing weary right now."

In Southern California, forecasters are warning of the threat of mudslides and rockslides in areas affected by both the Woolsey and Hill fires.

The National Weather Service said there's potential for travel delays on Wednesday afternoon into the evening along the Pacific Coast Highway and canon roads as a result.