WEST Australian police have been told confidential documents found in a Melbourne drug raid do not compromise police operations.

Files from ASIO, police and anti-corruption agencies were reportedly discovered on September 10 in the home of a suspected criminal thought to be in a relationship with a former official from the Office of Police Integrity, raising fears of a breach of national security and crime intelligence.

West Australian Premier Colin Barnett said yesterday the discovery was worrying, and the contents of the files would be looked into "very carefully".

"It is concerning that crime figures seem to have been able to obtain confidential and secret files relating to policing," Mr Barnett said.

Acting West Australian police commissioner Chris Dawson said yesterday his officers were liaising with Victoria Police about the confidential files.

"Preliminary information received indicates the WA police documents found in Victoria are 12 to 13 years old," he said.

"Information received from Victoria Police is that the person found in possession of the documents contends that the documents were used for training purposes and were not returned.

"Until WA Police can complete an assessment of the content of the documents reported to be found during a VicPOL drug operation, we are not in a position to make any further public comments about the matter."

The Australian understands that, based on information provided by Victoria Police, West Australian police are not alarmed. This is mainly because of the age of the documents.

It was reported yesterday that police were investigating whether the former head of intelligence and phone tapping at Victoria's Office of Police Integrity had stolen the documents.