Federal officials have outlined new steps Flint must take before switching its drinking water source again in the wake of its lead-contamination crisis.

The U.S. Environmental Protection Agency on Friday updated an order issued in January. It calls for Flint to build a three-mile interconnection so it can test water from a new authority for three months while continuing to provide water from Detroit's system.

EPA officials say Flint must also submit a new water treatment plan.

Flint is expected to switch to the Karegnondi Water Authority late next year and treat the water itself.

The city switched from Detroit water to the Flint River in 2014 to save money, but corrosive water caused lead to leach from aging pipes into homes.