Closed for the Duration : Damage: Nearly 10 months after the temblor, a shattered residence topples down a hillside. Cause is unknown.

One neighbor thought it was an earthquake. Another ran outside to see a rising cloud of dust. And when Elizabeth Zagarino finally looked down upon it Friday afternoon, she decided not to buy a home in this neighborhood.

Scattered more than one hundred feet beneath Zagarino’s feet were the remains of 3761 Glenridge Drive, a three-story townhome that inexplicably toppled down a hillside Friday after being red-tagged as uninhabitable for months following the Jan. 17 earthquake.

No one was injured in the incident.

“I have to tell you that this little neighbor here is causing extreme problems for the people up the hill trying to sell their homes,” said Zagarino, 26, of Studio City, who was out shopping for hillside homes with her realtor when they stumbled upon the site.

The incident, which occurred about 1 p.m., involved the first earthquake-damaged house to collapse since last March’s aftershocks, according to Los Angeles City Building and Safety Inspector Frank Bush, who visited the site.

“I have no idea what caused it to collapse,” said Bush, looking at the tilted wooden garage entry and yellow warning tape, the only remnants of the house left standing on the hillside.

But he did not rule out weather-related causes. “It could have been the rain or the wind,” he said.

According to Bush, the owner of the empty, 4,000-square-foot house was planning earthquake repairs to the foundation. Bush said the owner had been granted an extension to complete the repairs.

The reputed owner could not be reached for comment Friday. But neighbors had plenty to say about the downed townhome.

“I’m glad it’s gone, but I’m sad for the owner,” said Bob Brown, 50, who lives across the street. “This hill just can’t support that kind of building.”

Like many neighbors, Brown believed the home should never have been built at the location in 1987. Two other homes on Glenridge Drive were eventually torn down after the quake, he said, and city work crews have recently shored up the crack-lined side of the street where the home collapsed.

Bush said no other homes in the area are in immediate danger from the collapsed structure. He hoped to have an explanation for the collapse in the future, but could not speculate on whether there might be other quake-damaged hillside homes that could be collapse in the future.

A grove of walnut trees blocked the townhome, which crumpled into slabs of wood, concrete and insulation, from sliding into another house below, on Benedict Canyon Road.

The owner of that home, Fran Schrager, has not lived there since last spring, but had dropped by the house shortly after the incident with her children to pick up some ski jackets.

“Some lady just drove up by our house and said, ‘How’s your back door?’ ” said Schrager, who loaded her children into the car and raced up the hill to view the damage.

Looking down the hillside, the family spotted a yellow recycling bin among the rubble, prompting Schrager to wonder aloud who would clean up the destruction encroaching upon their back yard.

Her son, 10-year-old Alec, suggested that the owner of the disintegrated house “get his little toothbrush and clean this up.”