Investigations into an alleged NSW compulsory third party (CTP) fraud syndicate continue, with four more people arrested and charged.

With the support of the State Insurance Regulatory Authority, NSW Police formed Strike Force Ravens to crack down on fraud after CTP premiums spiralled.

Investigators have arrested 27 people and laid more than 170 charges in relation to a combined fraud of more than $11 million.

Last Tuesday detectives executed search warrants at properties in Pyrmont and Bass Hill, and a Bankstown medical practice. Investigators seized items including electronic devices and documents.

On the same day, a 45-year-old Bass Hill man was arrested and charged.

On Wednesday detectives arrested and charged a 36-year-old man at a home in Merrylands, a 40-year-old woman at a home in Cherrybrook and a 43-year-old woman at Castle Hill. Police allege the man and women fraudulently submitted CTP insurance claims.

The NSW Government says the fraud crackdown, along with reforms to the greenslip system, has reduced CTP premiums to an average of $495 – an eight-year low.