PORTLAND -- The homes of seven families living in Southwest Portland are off limits more than two days after ground underneath a residence at 6438 SW Burlingame Place became unstable, causing the home to slide down a steep hill and crash into two other structures below.

Kathy and Dave Hendrickson’s home is gone, destroyed after it slid from its perch on Burlingame Place down a hillside into the homes situated below, on Terwilliger Boulevard.

 More: 7 families displaced by house slide

Some sort of water system leak most likely caused the house slide.

Because the slide moved in such a specific and linear fashion, Portland State University head geologist Scott Burns said it appears to be a human-caused landslide.

Burns says the slide could have been a consequence of a leaking water main, sewer pipe or a breech in a two-year-old sprinkler system, oversaturating the soil and causing it to give way.

Water Bureau spokesperson Sarah Bott says the city was confident this catastrophe wasn't caused by any city-maintained pipes or systems.

 Slideshow: Ground scene | Sky 8 photos | Aftermath damage

 Interactive: View area, hear calls, see video

“This leak was not caused by a faulty water main or a city water system. We have very sophisticated leak detection. We went up there immediately and detected no leaks," she said.

KGW-TV Photo

An exposed sprinkler system pipe at the scene of Wednesday's house slide.

The home that did slide somehow came off its foundation just before 6 a.m., Wednesday, slid downhill and crashed into a home situated just below it.

“The people at the bottom were noticing water running down their driveways the day before. What does that tell me? There's a lot of water coming out someplace on the upper part of the slope -- that is a key fact,” Burns said. 

A natural gas worker thinks he saw a void in the street at the top of the slide. The city is testing that possibility.

While everyone works to determine how and why this happened, the city's water authorities are taking preventative measures to make sure unstable ground surrounding the slide area doesn't damage underground pipes, which could exacerbate the situation.

Officials need to shut off the water main underneath Burlingame Place. Any further soil settlement or movement could cause the 80-year-old main to break under pressure.

“We’re trying to take a pre-emptive measure that this main that’s doing fine right now doesn’t suddenly break or the slide keeps moving … so we don’t end up with a broken main pouring thousands of gallons of water and causing more damage,” Water Bureau Chief Engineer Mike Stuhr said.

The water shut off will affect 35 homes in the area and last a few hours, enough time for engineers to install shut-off valves on each side of the main.

Stuhr wouldn’t speculate on what caused or contributed to this house slide but did say his heart went out to the affected families.

Meanwhile, brave geo-technicians and insurance agents walked delicately on the debris, continuing their investigations.

One geo-technician says its going to take a lot of research into the history of land use out here before anyone can determine the cause of this slide.

Seven homes in the area have now been impacted by Wednesday's slide.

Sometime late Thursday city officials placed a yellow flag in front of the residence at 6434 SW Burlingame Place, just north of the house that slid.

The home on the other side has a red flag in front of it.

Red flags indicate the city has deemed it "unsafe" to enter these homes; yellow flags indicate homes have "limited entry."

Chaos following house slide

Neighbors heard the chaos as it escalated, then they heard wood creaking, crunching and snapping.

“It sounded like the garbage was going out, sliding across the street. Then I realized it was a lot more than that. I looked out the window -- we live right across the street from them -- and I saw the house, it just started to fall over backwards,” recalled neighbor Greg Sherwood.

Sherwood and several others called 9-1-1. A person can be heard screaming in the background of one of the calls.

Caller: "My next door neighbor's house just fell down the hill.

Dispatcher: "Your neighbor's house fell down the hill?"

Caller: "It fell down the hill! Kathy, get out of there!... I'm watching her, she's standing on top of the house."

Dispatcher: "How far did it fall?

Caller: "It fell down the hillside, oh, it's still going! Kathy, come on... Kathy!"

Six families evacuated their homes after the slide and authorities said the main road through the area would be closed off 'indefinitely' until they can be sure more homes won't slide.

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Neighbor Greg Sherwood told KGW he and another man helped rescue Kathy Hendrickson, who was alone inside her home when it broke loose.

Sherwood said Hendrickson heard noises and was trying to get out of the house when it began to slide and then fell backwards. He and a neighbor used a ladder to help get her off her fallen home.

Two other homes were hit before the sliding house came to a halt and amazingly, no one was seriously injured in either of those homes, either.

One of the homes that was struck actually moved off its foundation. The home came to a stop approximately 300 feet from its foundation on Burlingame, leaving a big, gaping hole where it once stood.

The houses have created such a scene that a Portland Fire and Rescue official said it was impossible to tell where one house ended and the others began.

Area remains dangerous for residents

At least a half-dozen homes have been evacuated in the area. No one in any of the other affected homes appears to have suffered injury, according to city officials.

Neighbors in this hilly area of Portland say landslides are nothing new. In 1996, during a particularly wet season, neighbors say that homes started making that eerie “snapping sound,” much like the one heard this morning, that signals a pending home slide.

 More: Geologists cite multiple factors causing slide

 Blog: What caused the slide?

 Map: Google map of slide location

People living here said when they heard the snapping boards and “popping trees” they began evacuating their own homes and gathered together outside. Then they began knocking on neighborhood doors and warning everyone else.

The only people who apparently were not aware of the calamity were those inside the affected homes.

Residents of the affected homes were clearly shaken and did not wish to be immediately interviewed, but did wonder where they’re going to stay in the short term.

Power, water, and gas utilities have been shut off in the immediate area. A section of Terwilliger Boulevard from Capitol Highway to Chestnut was also closed as a result of the slide.

More: Geologists map slides

City engineers are on the scene, according to Lt. Rich Tyler, who says "the earth is still moving."

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The hill continues to slide. Safety lines established by rescue crews have been moved back and are assessing soil stability in the area in order to give residents a timeline to return home.

Tyler says utilities will remain shut off until city engineers determine its safe to turn them back on.

"A large area will remain without power, water and gas," Tyler said.

Once utilities are able to locate and isolate the affected residences they will restore service on a "safe basis."