A short statement released by the Serious Fraud Office says it and the Reserve Bank are both investigating matters relating to CBL Insurance.

"The Serious Fraud Office and Reserve Bank of New Zealand are each investigating matters relating to CBL Insurance and associated entities," the statement says.

"The Reserve Bank is co-operating with the Serious Fraud Office investigation.

"The Reserve Bank is also co-operating with the Financial Markets Authority’s investigation relating to issues of market conduct and disclosure by CBL Corporation.

"No further comment on these investigations will be made at this time."