The National Guard is boosting its presence in Flint as part of an effort to assist in dealing with the city's drinking water crisis.

The state says about 70 guard members will be stationed Monday in Flint, more than double the earlier number in place. Officials say teams visited nearly 5,000 Flint homes Sunday, providing free bottled water, filters, replacement cartridges and water testing kits.

To improve water testing, the state says residents may drop off samples using official kits at five sites.

The water became contaminated after Flint switched from the Detroit water system to the Flint River as a cost-cutting move. The corrosive water lacked adequate treatment and caused lead to leach from old pipes.

On Saturday, President Barack Obama signed an emergency declaration.