The Japan Post Holdings Co. group has revoked the insurance-selling certificates of 75 post office workers for their improper sales of Japan Post Insurance Co. products, while reprimanding two others.

The insurance sellers encouraged customers to buy insurance contracts by giving them false explanations in violation of the insurance business law.

The group has been investigating 183,000 insurance deals that may have disadvantaged customers when they switched to new contracts.

The probe had found 3,608 law or internal regulation violations as of Wednesday, an increase of 575 from March 25, and that 2,619 post office workers were involved in the suspected contracts, up 409. The group will continue its probe on the remaining 400 cases.

Speaking a news conference Monday, Hiroya Masuda, president and CEO of Japan Post Holdings Co., said the group will be cautious about restarting insurance sales and will do so only after implementing systems to check customer contracts.