The slide has blocked the river, which is about 100 feet wide. It's changing the flow so now water is moving around the slide and cutting into residential property.
There are ten homes close to the slide but none were damaged by the slide.
"They're being told to be ready to evacuate should the river start to rise," said Chris Badger, Emergency Coordinator for the Snohomish County Department of Emergency Management.
They homes do not appear to be in immediate danger, but if the mud, trees and debris aren't moved out of the river and get it back to its normal flow, those houses could be in trouble. Heavy rain is also in the forecast over the weekend, which could add to the problem.
"We do have some concerns with the weather pattern coming in," Badger said. "With the river rising, the water won't have anywhere to go but through those neighborhoods."
The hillside north of the river collapsed Wednesday afternoon and the land continued to slide and shift for several hours, sending a massive amount of dirt, trees and rock into the river and surrounding land.
Badger said the county will be providing sandbags to the residents in the area and that county officials are working with various state and federal agencies to figure out what to do next.
"We are looking at different ways we can possibly dredge out to get the river to flow a different direction or back to it's old direction," she said, but added that there was no clear solution to the problem. "We hope to have some more answers for those folks tomorrow."
A community meeting with state and county officials is scheduled for Friday morning.