An email containing racist slurs against Aborigines has been circulated on the New South Wales police internal email system.

It makes reference to an Olympic games where a molotov cocktail is used at the opening ceremony.

The email has been received by 35 officers in four stations, including Bourke and Dubbo, in the state's west.

Some officers deleted it or reported it to their supervisors.

Police are now trying to determine if it was written by an officer or was sent from outside the service.

Deputy Police Commissioner Dave Madden has described the email as a "sick joke" and says officers may face charges or lose their jobs.

"For officers to be so stupid as to do this out in the western part of the state, and then to circulate among their peers, and then to find in some way that it's funny, it's just ridiculous," he said.

"That's why were are taking this matter so seriously.

"We are trying to find out who authored it, we are conducting an investigation and if we find the person we'll hold them responsible."