(Reuters) - Michigan authorities blocked county health officials from investigating an outbreak of Legionnaires' disease that may have been linked to the water crisis in the impoverished city of Flint, a county health supervisor told CNN on Saturday.

From June 2014 to November 2015 Michigan's Genesee County, which includes Flint, had 87 cases of Legionnaires', 10 of them fatal. The outbreak began weeks after a switch in Flint's water supply that also led to lead contamination.

Health and environmental officials have said the new water supply meant treatment changes that could have inadvertently led to a proliferation of Legionella, the bacteria that causes Legionnaires'.

But the root of the Legionnaires' outbreak was never determined and Genesee County Environmental Health Supervisor Jim Henry said that is because the Michigan Department of Environmental Quality blocked his office's attempts to get national health authorities involved.

"Our whole team was angry... You could see that there was a intentional, deliberate method to prevent us from doing our job," Henry told CNN on Saturday.

He said his office had urged involvement of the Centers for Disease Control, or CDC, but the DEQ prohibited further communication on the matter.

"They prevented that team from coming here and helping us to find the source," Henry said. After that, he said, there more cases of Legionnaires' in the summer of 2015, four of them fatal.

A CDC spokeswoman said the body was approached by Genesee County health officials in February 2015 about Legionnaires', but state officials told the agency they would handle the investigation themselves.

The head of Michigan's DEQ was fired over the Flint water crisis and Stephen Busch, a district manager in the drinking water division, has been suspended. Emails released to the public show Busch tussled with Henry over Legionnaires', saying it was premature to link the outbreak to the water system change.

Michigan's Republican Governor, Rick Snyder, has faced pressure to resign over the crisis and is scheduled to testify to Congress over the matter next month.

Asked for comment on the CNN report, Snyder's spokesman Dave Murray said, "There are a number of investigations into all that transpired, including a Flint Water Task Force created by Gov. Snyder. It would be inappropriate to get in front of that important work."

Flint switched its water supply from Detroit to the Flint River in April 2014 in a cost-cutting move when the city was under a state-appointed emergency manager. More corrosive water from the river leached lead from city pipes, causing a serious public health threat.

Legionnaires' disease can lead to severe pneumonia, respiratory failure, kidney failure and septic shock.

Reporting and writing by Fiona Ortiz.

To Learn More:

            Flint Official Warned Against Water Switch (by John Flesher, Associated Press)

Gov. Rick Snyder’s Top Officials Knew of Flint Water Link to Disease Surge 10 Months before Snyder Told Public (by David Eggert and Ed White, Associated Press)

Top EPA Official Resigns over Muted Response to Flint Water Contamination (by Timothy Gardner and Fiona Ortiz, Reuters)