Hundreds of rescue workers spent a sixth day searching the aftermath of the landslide in Washington state, navigating treacherous conditions as officials clung to fading hopes that survivors may be found.

But the coming news is expected to be bleak. The death toll is expected to rise “substantially,” Travis Hots, the Snohomish County District 21 fire chief, said in a news conference Thursday morning.

The confirmed death toll rose to 17 Thursday night after searchers recovered the body of an infant, officials said. Searchers had already located several more bodies, but they had not been recovered and cleared by the medical examiner’s office.

In addition, there are 90 people reported missing. While that number is down significantly from the 176 people authorities said were reported missing earlier in the week, it still points to the scope of how many lives may have been lost, how many people are still waiting for answers and how much is still unknown about the landslide’s true toll.

The landslide struck on a Saturday morning near the small town of Oso. It hit at the worst possible moment, authorities said, because on a weekday morning people may have been at work or school. Instead, people were home, contractors were coming to the area to do work and cars were passing through.

The slide area spans a square mile, with the debris field itself posing significant challenges to the workers trying to locate bodies. It may be as deep as 30 to 40 feet in places, according to the Washington State Department of Natural Resources. And it’s a mass of mud, piles of wreckage and spilled septic material and gasoline, creating tricky conditions for people attempting to search.

Some crews had been temporarily pulled from the slide area earlier this week because of concerns about additional slides, but there are no risks of that right now, said Steve Thomsen, the county’s public works director. “The slide’s stable right now,” he said.

More rain Thursday was expected to create additional challenges. As workers use their bare hands and shovels to dig through the wreckage, search dogs remain a key tool. It’s not a foolproof way to search, because they can pick up a scent that could be originating 50 feet away, Hots said, but it’s effective. If they think the dogs found something, they begin digging, bringing in machines if they can be safely used.

No survivor has been located since Saturday, the day of the slide. But workers continued to press on with an effort focused on rescue as well as recovery, even while they acknowledge that the odds of finding a survivor have dwindled.

“We’re not changing gears, we’re not changing the pace of this,” Hots said. “We’re going to exhaust all options to try to find somebody alive. If we just find one more person that’s alive, that’s worth it.”