An outbreak of Legionnaires' disease over the past 18 months has killed 10 people in the US state of Michigan, where officials are dealing with a major health crisis over lead-contaminated water.

The state's Department of Health and Human Services said on Wednesday that the outbreak dates back to summer 2014 and have not ruled out a link to the toxic tapped water in the of Flint.

"The state of Michigan is treating this situation with the same urgency and transparency as the lead response in the city of Flint," the health department said in a statement on the spike in Legionnaires' disease.

Officials said that since June 2014, there have been 87 confirmed cases of Legionnaires' disease, a severe type of pneumonia caused by bacteria, resulting in 10 deaths.

The illnesses occurred in Genesee County, where Flint is located.

Officials said that nearly half the people sickened with the disease were exposed to water in Flint.

The crisis from lead-poisoned water came after state authorities ignored months of health warnings about foul-smelling water in Flint.

State officials in April 2014 had begun drawing water for city residents from the Flint River, rather than continuing to buy it from Detroit.

Since then, the northeastern city of some 100,000 people has seen lead levels surge and a plague of issues after drinking and bathing in the cloudy, foul-smelling coming out of their faucets.