It's understood the investigation is looking into how and why the Independent Commissioner Against Corruption's office awarded several supply contracts.

"NT Police are investigating an historical matter involving the Office of the ICAC," a police spokesman said in a statement on Thursday.

"No current staff are being investigated.

"As this investigation is ongoing no further detail will be provided".

Chief Minister Michael Gunner confirmed allegations had been made against the NT ICAC, but he said they occurred under the previous commissioner Ken Fleming QC.

"We have a new independent commissioner against corruption and we need to give him time to do his job," he said.

"He has previously worked in an ICAC and he has a strong background on how ICACs do their jobs."

Asked if the public had lost confidence in the office, Mr Gunner said the NT ICAC was reasonably new and issues were to be expected.

"I don't believe there's a loss of confidence. I think we just need to let the new ICAC do his job".

The new commissioner Michael Riches was appointed in July and has previously said he would cooperate with any investigation.

He also said public confidence was fundamental to the NT ICAC's success.

The NT's ICAC started in November 2018.

The office has been contacted for comment.

Australian Associated Press