South-bound lanes on State Highway 1 near Porirua have reopened on Tuesday after a truck crash that caused a chemical spill alert about 5am.
Porirua Fire Service station officer Trevor Sheehan says the truck and trailer unit was carrying general cargo and numerous chemicals, including two small containers of "a very dangerous chemical".
Emergency workers closed the south-bound lanes and traffic was diverted through the suburb of Tawa for most of the day while a crane was brought in.
Mr Sheehan said the situation was under control by midday, with the trailer unit righted and emptied, and all chemicals accounted for with no spillages.
The driver of the truck escaped with minor injuries.