The Minnesota Department of Corrections has hired a new firm to oversee medical care in state prisons, severing a 15-year relationship with a corporation that became the target of lawsuits and staff complaints alleging substandard care.

Since 2000, under Corizon Health Inc., the state prison system has had at least nine inmate deaths and numerous injuries related to poor and delayed care, according to a 2012 Star Tribune investigation.

Although Corizon was the lowest of three bidders, the department said Thursday that it has signed a two-year contract with Centurion Managed Care, a national health care company that it claims will provide innovative approaches to preventive and mental health care for the state's roughly 9,000 inmates.

Centurion is expected to "deliver significant savings to taxpayers while improving the quality of care for offenders," Corrections Commissioner Tom Roy said in a statement.

The contract is worth $67 million and takes effect Jan. 1. Corizon's bid was $115,600 below Centurion's.

Centurion is owned by Centene Corp., a publicly traded company based in St. Louis, Mo. Earlier this year, Centurion signed contracts to manage prison medical systems in Tennessee and Massachusetts.

The company bills itself as "The Next Generation of Correctional Healthcare. Today."

The contract with Centurion apparently does not specify daily prison staffing levels, an issue that under Corizon was a constant complaint among prisoners and their families, some corrections officers and a field of attorneys who have brought neglect cases against the state.

A staffing matrix attached to the new contract shows only the number of hours — but not the shifts — that Centurion medical staffers will be working at each of the state's nine correctional facilities.

Department spokesman John Schadl said such details will be worked out in the next few months.

Minnesota's contract with Corizon called for the company to staff prisons with a doctor only until 4 p.m. on weekdays and with minimal nursing coverage until 11 p.m. That left one on-call physician to handle overnight medical problems by phone for the entire state, and occasionally forced prison staff to make urgent medical decisions late at night.

In a statement issued at the time of one legal action last year, the company said: "Corizon's current coverage meets the need to provide the community standard of care. Corizon is committed to delivering services in a safe, efficient, cost-effective manner.''

Roy said Centurion has a strong history of delivering mental health services to offenders, a population in which behavioral disorders are widespread.

"The complex nature of these offender populations requires careful collaboration between DOC behavioral health staff and contract providers of psychiatric services," Roy said in a statement.

Under the contract, an additional level of on-call psychiatric coverage will be provided around the clock.

Roy also said the department expects to see savings in the way medications are provided to offenders via a computerized dispensing system, allowing nurses to put more focus on care.