The NZ Transport Agency has announced that the reopening of State Highway 1 Brynderwyn Hills, initially scheduled for May 13, has been delayed until the end of June due to two significant slips on April 26 and 30.

Despite the setback, NZTA and its contractors are working urgently to find a solution.

"Our priority has been to undertake geotechnical and safety assessments to determine the best option for stabilising the hillside and getting State Highway 1 Brynderwyn Hills open as quickly as possible," said NZTA National Manager of Infrastructure Delivery, Mark Kinvig.

Excavation has begun, with operators working from a platform at the top of the ridge to remove up to 55,000 cubic meters of earth and stabilise the site.

The team is working seven days a week, weather permitting, to get the road open.

While the closure is in place, NZTA is proactively monitoring the three official detour routes to ensure they are safe and of high quality.

Essential repairs will also be undertaken on these routes.

The agency thanks everyone for their patience and reminds people to drive safely when using the detour routes.

NZTA will keep the public updated through their e-newsletter and social media channels as they work to complete the recovery works as quickly as possible.

However, if there is a significant amount of unexpected rain or further instability is found, the reopening timing could be delayed.