Boulders the size of pickup trucks crashed down on weekend hikers on the hairpin turns of a trail near Yosemite Falls, killing three and injuring seven, park officials said.

The rock slide, onto the 4.8-mile trail about a half-mile below the top of the famed 2,700-foot waterfall, left a "big blank space" on the face of the mountain, said Mary Niles, librarian at Yosemite National Park. Debris was scattered over a 600-yard section of the tortuous trail.

About two dozen hikers were on the trail when the slide rumbled down yesterday, said Linda Abbott, a National Parks Service spokesman.

The body of one of the dead hikers was removed by nightfall, and the other two were to be removed today, park officials said.

Mike Rover, a security officer for the park's concessionaire, said he heard a "big rumble" and rushed from his Yosemite Valley office.

"I looked over there and saw a boulder rolling down slowly. It seemed about the size of half a house," he said. ". . . There was all kinds of dust. aThe dust cloud extended from the lower falls to almost the top of the upper falls," a distance of about a half-mile.