More than 5km of State Highway 6 near Nelson is covered with diesel after a spill which caused two minor crashes.
The large spill is affecting the southbound part of the highway from Haven Rd to Whakatu Drive in Richmond and police have asked motorists to avoid travelling in the area while the fire service and council contractors clean up the mess.
No one was injured in the crashes.
Traffic is being diverted through Stoke and drivers should use Waimea Rd to get from Nelson to Richmond, a police spokesperson said.
Emergency services are still trying to figure out the source of the spill and police say motorists should be alert because the diesel may have been spread to other areas.
