Scientists believe low oxygen levels are the most likely cause of the large number of deaths among marine animals in Marovo lagoon in Solomon Islands.
From early this month locals reported seeing dead creatures including fish and crocodiles in the lagoon.
The co-ordinator of the Secretariat of the Pacific Community office, Mia Rimon, says scientists are still on the ground but have a good idea what caused the deaths.
She says they think there's been a process of algal blooms dying-off, resulting in oxygen depletion.
She says her office and the Secretariat of the Pacific Environment Programme have offered assistance.
"Scientific technical assistance, for some resources with immediate relief, things of that nature, putting in fads to help to secure food security for the people who have lost their fishing grounds."
Mia Rimon says recent mangrove culling could have contributed to the algal bloom crash.