VICTORIA -- The Western Vancouver Island communities of Tofino and Ucluelet will remain cut off from the rest of the island overnight after an early-morning rockslide closed Highway 4 in both directions.

The obstruction is at Kennedy Lake, roughly 15 kilometres from Ucluelet, where construction crews have long been working to upgrade the precarious highway pass.

The B.C. Ministry of Transportation says that crews were conducting a scheduled controlled blast in the area, which resulted in a “larger than anticipated rockfall” spilling onto the road.

Ministry of Transportation crews and geotechnical engineers are currently on scene assessing the damage, calling it a "major road failure."

At 3:30 p.m., the ministry said in a statement that the roadway will remain closed overnight.

"We do not have an estimated time for reopening at this point," the ministry said.

"Rock embankment fill is actively being hauled and placed to build the damaged road area back up to highway grade."

Tofino Mayor Josie Osborne told CTV News the rockslide knocked out a large retaining wall, leaving many residents and travellers stranded.

"We are cut off from civilization – or maybe it's that civilization is cut off from us – but the road is closed and there's no traffic access from the West Coast," Osborne said.

Travellled through the rainstorm to make it home last night - now the world is cut off from us. #BCHwy4 is closed ‘til 5pm due to rock on the road at Kennedy Hill - please follow ⁦@DriveBC⁩ and visit https://t.co/927IbuvL8y for updates. #tofino #ucluelet #portalberni pic.twitter.com/lmQu4XsOJa — Josie Osborne (@Josie_Osborne) January 23, 2020

"With a complete closure like this we're looking at using a helipad at Tofino hospital in case of an actual life-threatening emergency," Osborne said.

Traffic control personnel are turning drivers around at the Tofino-Ucluelet junction and at Sproat Lake.

In July, blasting in the same area caused several large boulders to fall onto the roadway, closing the highway for several hours.

The latest information on the road closure is available on the DriveBC website.