An unstable chunk of hillside in the upscale La Jolla neighborhood slipped another five or six feet Thursday afternoon, shoving into already-damaged houses at the bottom of the slide zone.

The city has been rushing to stabilize the street of million-dollar homes since the initial collapse in October sent a 200-foot-long section of earth 20 feet downhill.

"It's not uncommon for this to happen as you're making those repairs in a landslide zone but it's still a setback," said San Diego Mayor Jerry Sanders in a news conference at the site.

Workers were preparing to drive giant steel pins into the toe of the slide zone when the land began to shift again. Pins have already been positioned 60 to 65 feet deep along the lip of the collapse on Soledad Mountain Road to hold the rest of the earth in place while repairs and reconstruction proceed.

City spokesman Bill Harris said it's not clear how much additional damage the new collapse has caused to houses at the bottom of the slide zone.

There were no reports of injuries.

Six houses were uninhabitable after October's collapse. Residents have blamed the city for not recognizing the threat after cracks appeared in the street above. It caused an estimated $48 million in damage.

The hillside has given way in the past. At least three significant slides occurred between 1961 and 1994, including a major 1961 failure that destroyed seven homes under construction.