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Connecticut's financially "unstable" Obamacare health-insurance co-op was placed under state supervision on Tuesday, as regulators said 40,000 people covered by the company will ultimately have to find new plans for the coming year. HealthyCT is the 14th of 23 original Obamacare co-ops to fail since they began selling health plans on government-run Affordable Care Act insurance exchanges. Several of the other remaining co-ops, at least, are believed to be on shaky financial ground.

Until last week, the nonprofit HealthyCT had "adequate capital and sustainable liquidity" — but that fell apart Thursday with a federal requirement that hit HealthyCT with a $13.4 million bill, according to the Connecticut Insurance Department.

State Insurance Commissioner Katharine Wade said that the resulting "hazardous financial standing" of HealthyCT led her to place the co-op under supervision, which prevents the company from writing any new policies, and also from renewing any large or smaller employer plans that expire after last Friday.

The co-op covers about 13,000 people on plans sold on Connecticut's Obamacare exchange, who represent about 10 percent of all the Obamacare plans sold in the Nutmeg State. And another 27,000 people are covered by HealthyCT through large and small employer plans.

All exchange customers will remain fully covered through the end of 2016, but then must find a new plan for 2017 when open enrollment begins Nov. 1, since HealthyCT "will no longer be offered," according to the Connecticut Insurance Department. For employer plans, the co-op is now barred from writing any new business or renewing any existing business effective Aug. 1. HealthyCT group plans that renewed July 1 will have coverage through June 30, 2017, from the co-op. After that, the insurance department said, it "will work closely with HealthyCT, the state exchange Access Health CT, the broker community and other carriers to help large and small employers find new coverage when it comes time for them to renew their plan annually." The head of the state's Obamacare marketplace, Access Health CT, said it is developing a plan to inform customers of HealthyCT who purchased plans through that exchange "of their change in status and to inform them that they will need to shop for a new plan come November."

Wade said HealthyCT's financial health became "unstable" by a federal requirement issued last week that the co-op pay $13.4 million to the U.S. Department of Health and Human Services as part of Obamacare's risk adjustment program, as well as a related Obamacare program called risk corridors.

The risk adjustment program is designed to spread out the financial risk of insuring people with Obamacare plans by redistributing money from insurers with healthier customers to companies with sicker customers. But smaller insurers, particularly co-ops, have sometimes been strained by the program because their balance sheets are not large enough to cover the costs from it.