A judge on Thursday ordered delivery of bottled water to lead-tainted homes in Flint, Michigan, unless residents opt out or officials verify that a water filter has been properly installed.

Water is distributed for free at many sites in Flint. Residents who can't get to a distribution site can call a community group for help, but U.S. District Judge David Lawson said it's still not enough.

"The fact that such items are available does not mean that they are reliably accessible or effective in furnishing safe drinking water to every household," he said. "Bottled water is heavy, and not all of Flint's residents are capable of transporting the cases of water effectively."

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Flint residents are urged to use bottled water or filtered tap water while the city's water system heals from lead contamination. Corrosive water from the Flint River wasn't treated properly for 18 months.

It's unclear how many people in the city of roughly 100,000 will get home delivery. Lawson said the state of Michigan and Flint must provide each home with four cases of bottled water per week per resident, if they qualify.

Delivery isn't required if officials confirm that a filter has been installed and is working properly. Residents also can decline water.

State attorneys were reviewing Lawson's order, said Anna Heaton, spokeswoman for Gov. Rick Snyder.

"What the judge said is very reasonable," said Dimple Chaudhary, an attorney with the Natural Resources Defense Council, which sought the injunction along with the American Civil Liberties Union of Michigan. "It's a complex situation, and the government response has not been robust enough."