The off-ramp connects Kalaniana'ole to Kamehameha Highway at Castle Junction, and the cliffs above it have been identified by the state Department of Transportation as a high-risk area for landslides.

Officials closed the off-ramp yesterday after 30 cubic yards of dirt and rocks fell onto the road about 4 a.m. They thought they could reopen the off-ramp but changed their minds after rocks ­ some as big as softballs ­ fell from another area of the cliffs about 2 p.m., said Scott Ishikawa, transportation department spokesman.

No one was injured and no property damaged by either incident. Debris from the cliffs also came down May 20 and 23.

"We are going to keep that thing closed until we figure out what we want to do," Ishikawa said. "It could be for days. But safety comes first."

Engineers hiked to the top of the cliffs today to see how stable they were, Ishikawa said.

The land may belong to nearby Hawai'i Pacific University and no work will begin until ownership and liability issues are settled, Ishikawa said.

The state recently identified the Honolulu-bound lanes of Kalaniana'ole Highway at Castle Junction to be at the fifth-highest risk of rockfall among 66 O'ahu highway sites. The state noted that high, steep slopes of volcanic rock above the highway are highly deteriorated and there is no rockfall catchment in the area, where traffic is heavy.

Solving the problem could cost $6 million, according to "a very preliminary estimate," Ishikawa said.

Drivers can still get onto Kamehameha Highway by making a sharp right turn off Kalaniana'ole at the intersection.

Some drivers, however, ignored the orange safety cones and used the off-ramp yesterday, Ishikawa said. Barriers were set up to prevent that, he said.

"It was kind of frustrating," Ishikawa said. "We are trying to seal off an area we feel is hazardous. We're asking people to be patient."