Several state highways remain closed across the South Island this morning following heavy rain, slips, a crash and a diesel spill.

An NZTA spokesperson said State Highway 67 remained closed between Hector and Mokihinui because of a slip, with motorists being advised to delay travel if possible.

State Highway 65 was also closed between O’Sullivans Bridge and Springs Junction because of slips and flooding.

A detour was available for southbound traffic via State Highway 6 to Inangahua, Brown Creek Road, State Highway 69 to Reefton and State Highway 7 to Springs Junction, with the reverse route for northbound traffic.

The spokesperson said State Highway 6 between Murchison and Kawatiri was closed because of flooding, with motorists again being urged to delay their journeys if possible.

Further south, State Highway 6 remained closed between Makarora and Lake Hāwea following multiple recent slips.

Escorted convoys were operating through the affected section three times a day.

The first convoy leaves Makarora village heading south at 7.15am before returning north from the Isthmus Peak Track car park at 8am.

A second convoy leaves the Isthmus Peak Track car park heading north at midday and returns south from Makarora at 12.45pm.

The final convoy leaves the car park heading north at 5.30pm before returning south from Makarora village at 6.15pm.

In Canterbury, a crash north of Ashburton closed State Highway 1 between Racecourse Road and Mitcham Road.

A detour was in place using Racecourse Road, Hepburns Road and Mitcham Road.

In Otago, a diesel spill closed State Highway 1 north of Dunedin between Evansdale and Hawksbury.

A detour was available via Coast Road, although NZTA said it was not suitable for heavy vehicles.

Motorists were being urged to take extra care in affected areas.