A substance leak at Picton Wharf is causing delays for Cook Strait ferries this morning.

An exclusion zone is in place around the KiwiRail yard, while cordons are around the entrance to the wharf.

Fire and Emergency have been called to identify a substance that’s leaked, how much, and what the best course of action is.

A number of crews are on site - including a Hazmat truck.

The issue was detected in the yard around 2am, as a container was about to be transferred to a ship.

More to come.