Investigators are appealing for witnesses after a boat capsized near Kaikōura, killing five people.
Members from the Nature Photography Society of New Zealand were onboard the chartered vessel when it overturned in Goose Bay on Saturday.
Kaikōura mayor Craig Mackle said he believed the accident happened after the boat collided with a whale.
"We have an upturned boat tipped over by a whale from what we can understand, came up from underneath."
And Goose Bay local Kevin Anderson told the NZ Herald he saw a whale diving underwater "two or three hundred yards" away from the boat shortly after the Coastguard arrived at the scene.
"Terrible, terrible, terrible tragedy that's just out of the blue, there's nothing you can do," he told the NZ Herald.
On Sunday the Transport Accident Investigation Commission (TAIC) asked for any witnesses to the incident to come forward.
"The Chief Investigator, Naveen Kozhuppakalam wants to hear from anyone who saw or recorded what happened - before, during or after the incident," a spokesperson said.
"The Commission investigation will run alongside investigations from other agencies. Two investigators are assigned to secure evidence, talk to witnesses, examine any electronic evidence available and look at the circumstances of the incident."
The best way to share information is to email TAIC at info@taic.org.nz.
Maritime NZ said in a statement investigators will work alongside NZ Police and TAIC.
"The exact circumstances surrounding the incident are still to be established. No further information is available at this time. We will assess the information gathered and decide the next steps."
On Saturday Maritime NZ said they sent two investigators from Christchurch to Kaikōura and any investigation activity will commence after rescue and recovery operations have concluded.
"Maritime NZ offers its heartfelt condolences to the family and loved ones of the people who have died in today's incident," Maritime NZ principal investigator Tracy Phillips said.
"We'll be conducting a thorough investigation under the Health and Safety at Work Act and the Maritime Transport Act and we'll do everything we can to support NZ Police in their investigation."
