WASHINGTON — Efforts to recover bodies following a Washington state mudslide that killed at least 29 people could be hampered in the coming weeks if melting snow runs into a clogged river at the disaster site, officials said.

Over the past few days, workers at the mud pile in the foothills of the Cascade Mountains, northeast of Seattle, have taken advantage of sunny skies and receding water, but more rain is expected from Thursday through Sunday.

The official death toll from the mudslide, based on the number of victims’ remains sent to the coroner’s office, rose to 29 on Wednesday, up from 28 a day earlier, the Snohomish County Medical Examiner’s office said. On Tuesday, 20 people were still listed as missing.

The March 22 slide was triggered when a waterlogged hillside caved in above the Stillaguamish River. A torrent of mud roared over the riverbanks and across state Highway 530, engulfing some three dozen homes on the outskirts of the town of Oso.

The mudslide clogged the Stillaguamish River, which in the following days cut a slow-moving channel through the mud and debris. But snow melting on the Cascade Mountains is expected to pour through that channel, possibly flooding the mud-pile site.

Sections of the slide area, already under 25 feet of water and believed to contain human remains, could be submerged by more than 100 feet of water within three to four weeks without a channel to divert the partially dammed river, said Mike Asher, an area fire chief acting as the head of operations for the east side of the disaster zone.

The U.S. Army Corps of Engineers is working on a plan to dig a river channel, likely to be accompanied by levies, to keep the muddy, contaminated disaster site cordoned off, Asher said.

The Snohomish County Medical Examiner’s Office said 22 of the confirmed fatalities have been identified, including a 4-month-old girl and two other children aged 5 and 6.