Last year, officials overseeing New Jersey's employee health plan — which covers the state's teachers, cops and other public workers — discovered something that made no sense. The state had been billed $674,856 for a patient's care at NewYork-Presbyterian. But it had paid $2,026,524, some three times what it was charged.

It wasn't an isolated incident either. A review by the state's Treasury department of the 50 biggest out-of-state hospital claims in 2020 showed the state paid millions in excess of what was actually billed, even though New Jersey's contract with insurer Horizon Blue Cross Blue Shield of New Jersey explicitly bars overpayments. Efforts by those inside the state government investigating the payments were thwarted by the insurer, documents show. And today, neither the state nor Horizon are saying where that money wound up, leaving open questions about where the state's money went and who may have profited.