The damage done by the recent slip in Manawatu Gorge is clear to see. MURRAY WILSON /FAIRFAX NZ

The Manawatu Gorge will remain closed until at least the middle of the year, the New Zealand Transport Agency announced today.

A series of landslides on August 18 last year has closed the State Highway 3 road through the gorge for all but three days.

NZTA initially thought the road could be reopened this month but, during a site visit this morning, State highways manager David McGonigal said it would not be opened until later this year.

"The sheer size and complexity of the job requires more time, and our best estimate to reopen is midway through this year."

Mr McGonigal earlier told the Manawatu Standard that crews working on the slip site had encountered increasing amounts of rock.

"It's much more difficult and time-consuming to shift rock than dirt . . .'' he said. "The silver lining is that it's shedding more light on the geological makeup of the slope, and the more solid rock that we find, the more secure it's likely to be.

"However, the rock we've uncovered so far is quite fractured, so benching the hillside remains the linchpin of keeping the slope stable in the long run.''

"The third bench is nearly done and we expect to start cutting the fourth bench next week, '' he said.

The Saddle Rd and Pahiatua Track have been used as alternate routes while the Gorge Rd is closed.