The source of spilled chicken offal on an Auckland motorway is a mystery, police say.

The southbound southern motorway between the Papakura and Drury interchanges was closed until around 3am on Saturday while contractors cleared the mess.

Police said there was “no indication” about where the innards had come from as the spill was only reported after the fact. 

The road has since reopened, according to New Zealand Transport Agency. 

However it could still pay to keep your windows rolled up.