Japan’s financial regulator penalized the country’s largest property and casualty insurers for colluding to fix prices in contracts with corporate clients.

The Financial Services Agency has issued business improvement orders on the core units of Tokio Marine, MS&AD Insurance and Sompo, said Finance Minister Shunichi Suzuki at a briefing on Tuesday.

The investigation has rocked Japan’s casualty insurance sector, which has also been under fire for failing to detect fraudulent auto insurance claims. The three groups command about 90% of the entire market worth roughly ¥9 trillion ($63 billion) in annual net premium revenue, according to data by the industry association and companies.