A large diesel spill has led to a number of crashes on State Highway 6 on the outskirts of Nelson.
The police are advising motorists travelling between Richmond and Murchison to take extreme care due to the spill.
It's not yet known what caused it, but the spill stretches south from Richmond for a considerable distance.
A police spokesperson, Barbara Dunn, says several minor crashes have been reported and drivers must take extreme care.
She says contractors have been called in to deal with the spill, but the work may take several hours.