SAN FRANCISCO - About 150 residents of San Francisco's North Beach district were forced into the streets Tuesday morning after a landslide sent rocks and boulders tumbling down onto at least one apartment building.

The hillside collapsed a little after 3 a.m., closing a main thoroughfare through the city but causing no injuries, authorities said.

City engineers were assessing possible damage as a massive pile of boulders and mud lodged against an apartment building and a night club at the bottom of the hill.

A 45-unit apartment building at the top of the hill was evacuated.

Authorities were trying to determine what caused the slide.