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FLINT, Mich. (AP) — Michigan environmental experts warned that Flint's water system had "significant deficiencies" just weeks before Gov. Rick Snyder announced an end to bottled water service that was introduced to allay a lead-tainted water crisis.

A surface water treatment engineer detailed 10 unresolved issues in a March 21 letter to Flint Mayor Karen Weaver. The letter said that the Michigan Department of Environmental Quality has no confidence in Flint's capacity to manage the system.

Snyder announced April 6 an end to free bottled water distribution, citing two years of testing showing Flint is below the federal action level for lead.

Flint is recovering from its lead-contaminated water crisis and producing "very high quality drinking water," said Tiffany Brown, a spokeswoman for the state's environmental department.

"The department's concern is the ability of the city to maintain that," Brown said. "The treatment plant is not adequately staffed and is being supplemented by a short-term contract."

Brown also noted the viability of the water system's funding and whether the city can adopt a rate structure that will support operations.

Michigan's environmental agency is working with the Flint to ensure that its water system is maintained, said Snyder's spokeswoman Anna Heaton.

Senate Minority Leader Jim Ananich is among many who have pushed for the bottled water service to continue until home water lines are replaced, which could take until 2020.

He said Snyder's administration has struggled to rebuild trust since 2014, when it wrongly assured Flint residents that water provided from the Flint River was safe to drink.

"The state forced the shift (in water source) and caused the crisis," Ananich said. "To say, 'mission accomplished,' is not accurate."