DETROIT (Reuters) – State government officials knew about an outbreak of Legionnaires’ disease and its suspected link to contaminated water in impoverished Flint, Michigan, at least 10 months before a public announcement was made, documents released on Friday showed.

The disclosure of the documents, among thousands of pages of emails and other material released, comes as Michigan’s Republican Governor Rick Snyder faces pressure to resign over his administration’s handling of the Flint water crisis.

Michigan’s Genesee County, which includes Flint, had 87 cases of Legionnaires’ from June 2014 to November 2015, 10 of them fatal.

Flint’s water supply was contaminated by lead, a serious public health threat, after its water supply was switched from Detroit to the Flint River in April 2014 in a cost-cutting move when the city was under a state-appointed emergency manager.

Friday’s documents echoed previous disclosures showing that high-ranking state officials knew about an increase in Legionnaires’ disease in Genesee County and a possible link to Flint’s water 10 months before the governor said he got information about the outbreak.

Stephen Busch, a district manager in the drinking water division for Michigan Department of Environmental Quality, wrote in an email on March 17, 2015 that the city should take action to optimize water quality to help limit the potential for occurrence of Legionella, the bacteria that causes Legionnaires’.

Emails also show Busch tussling with county health officials over the issue and saying it was premature to link the public water system with Legionella. Busch was suspended last month and his job status is currently on review, a state official said.

The U.S. Centers for Disease Control and Prevention was approached by Genesee County health officials in February 2015 about an increase in reported Legionnaires’ disease cases, but state officials subsequently told the agency they would handle the investigation into the matter themselves, a CDC spokeswoman said.

In January 2016, state officials asked for the CDC’s help in the matter.

Liberal group Progress Michigan said Friday’s release of documents and emails was all for show, and called on Snyder to release those of his and his executive staff’s.

“If the governor is serious about wanting to be transparent, he will release every single document and communication regarding the Flint Water Crisis, including those of his executive staff,” Lonnie Scott, executive director of Progress Michigan, said in a statement.

Flint, a predominantly black city of about 100,000 people, switched back to Detroit water in October after tests found high levels of lead in samples of children’s blood. Water from the Flint River was more corrosive and leached more lead from the city pipes than Detroit water did. Lead can damage the nervous system.

Snyder, who has apologized for the state’s poor handling of the water crisis, alerted the public to the Legionnaires’ outbreak on Jan. 13 and said he had only heard about it two days earlier.

“Gov. Snyder first became aware of the Legionnaires’ Disease outbreak in mid-January of this year,” his press secretary Dave Murray said. “He’s made it clear that he wants to be made aware of such issues more quickly, and already made some changes in some state departments.”

On Friday, a U.S. House of Representatives oversight panel said Snyder would testify on the Flint water crisis next month. Darnell Earley, who was Flint’s state-appointed emergency manager when the city switched from Detroit’s water system, will also testify.

Snyder said in a Friday statement in which the state released emails and other documents from several state departments that “all levels of government failed the people of Flint. This crisis never should have happened.” He said by making the documents public, anyone could review them.

The Legionella bacteria is found in certain plumbing systems, including hot tubs, humidifiers, cooling towers and hot water tanks. Legionnaires’ is spread by breathing in mist from water, and cannot be spread from person to person.

(Additional reporting by Dave McKinney, Fiona Ortiz, Karen Pierog, Karl Plume, P.J. Huffstutter and Justin Madden in Chicago, David Shepardson and Timothy Gardner in Washington; Editing by Phil Berlowitz and Tom Brown)