Cook Islands police are investigating how a weekly newspaper in Rarotonga is getting secret Cabinet papers and often releasing the information before it is discussed by ministers.
The Prime Minister' Office Chief Executive Officer, Piho Rua, says there's some indication that the information is coming from the office of a certain member of parliament.
Mr Rua has interviewed a number of staff in the Prime Minister's Office and all have denied responsibility.
The investigation follows disclosure by the Cook Islands Herald of travel costs incurred by Deputy Prime Minister, Sir Geoffrey Henry, to attend a recent Asian Development Bank meeting in China.
A ruling by the former speaker of parliament make all travel costs of politicians secret.