Firefighters have cleaned up a chemical spill at Picton's Port Marlborough.
Crews, including a Hazmat unit, were called in from Nelson to assist at about 2:20am on Thursday.
The port was cordoned off and closed, and there were no reports of injuries.
Interislander executive general manager Walter Rushbrook said all ferries to and from Picton were delayed but resumed at 7:30am.
He said the leak possibly came from a customer's container.
"After a thorough check of the container and consultation with the customer, it was determined everything was safe and normal operations resumed at 7:30am," Rushbrook said in a statement.
"Aratere and Valentine are running on schedule this morning.
"Kaiarahi was delayed overnight due to the incident. The Kaiarahi 8:45am sailing out of Wellington is now expected to depart early afternoon."
Customers travelling on Kaiarahi would be contacted directly about the delays, Rushbrook said.
