A fatal mudslide in Washington state over the weekend killed several people, sent others to the hospital and left a trail of devastation and uncertainty in its wake. Many people remain missing. Here’s everything you need to know.

What happened?

A landslide on Saturday morning in the northwest corner of Washington state killed at least 14 people and demolished several homes. The slide was first reported to authorities at around 10:45 a.m.  (local time).

The U.S. Geological Survey said that the landslide was caused by recent rain conditions that had saturated the soil. Debris from the landslide covered nearly a full mile of State Route 530, hence the hashtag #530slide. In addition, it created a blockage at the North Fork of the Stillaguamish River, creating a flood hazard, the USGS said. The U​SGS and the National Weather Service are working to see what would happen if this blockage at the river broke, helping to figure out about where flooding could occur.

There’s still a risk of flash flooding in the area, though the National Weather Service says the situation around the Stillaguamish River seems to be stabilizing. (Some flooding is still occurring upstream of the slide, with flash flooding a possibility downstream.) A state of emergency has been declared due to the severity and breadth of the slide.

How many people are dead? How many people are missing?

At least 14 people were killed, authorities said Monday evening. Three people were confirmed dead on Saturday, five bodies were found on Sunday and another six bodies discovered Monday.

Officials said during a press conference Monday evening that 176 names were on the list of people missing or unaccounted for after the mudslide. But they cautioned that the list of missing people is expected to “decline dramatically,” as it contains all reports of people who may or may not have been in the area, reports that range from the specific to the vague. (Head here for more on this number.)

Rescue workers are using thermal imaging cameras to search for people amid the debris, while helicopters are surveying the site from above. The rescue effort is complicated by the conditions of the ground itself, as workers wade through mud, debris and other wreckage. “We have this huge square-mile mudflow that’s basically like quicksand,” Snohomish County Fire District 21 Chief Travis Hots said, according to the Associated Press. On Monday, some ground rescue crews had to pull back from the area due to concerns about “additional slide activity” in the area, the county said.

At least eight people have been taken to area hospitals. As of Monday afternoon a six-month old baby boy and three adult men remained in the intensive care unit at Harborview Medical Center in Seattle.

Where did this occur?

Near Oso, Wash., about an hour north of Seattle:

How big was the landslide?

This particular landslide is about one square mile and up to 15 feet deep in places, according to Snohomish County officials.

The slide wiped out a considerable chunk of land:

You can see some of the destruction in this video posted by the Snohomish County Sheriff’s Office:

What can I do if I know someone in the area and want to see if they’ve been found or report that I haven’t been able to reach them?

Visit www.safeandwell.org or call the Snohomish County Department of Emergency Management call center at 425-388-5088. (Officials warn that you may have to wait a little while for someone to answer.)

What are landslides? What causes them?

Landslides cover a variety of ground movements, including rock falls, debris flows and failing slopes, according to the U.S. Geological Survey. They’re largely caused by the combination of gravity and an over-steepened slope, but they can also be caused by overly-saturated rock or soil following heavy rain or snowfall (as authorities believe to be the case in Washington), volcanic eruptions and earthquakes.

Are landslides common?

Landslides occur in every state, though the U.S. Geological Survey says the Appalachian Mountains, the Rocky Mountains and Pacific Coastal Ranges have “severe landslide problems.” Slides cause from $2 billion to $4 billion in damages and from 25 to 50 deaths each year in this country, according to the USGS.

This post will be updated as more details and information become known. Latest update: Monday at 10:32 p.m.