The state health department said there have been two cases of Legionnaires' disease related to McLaren Flint Hospital within the last six months, but the hospital said that's not the case.
State officials are demanding that the hospital change the way it tests and monitors its water after finding problems with its testing.
The hospital will have to provide data and documents for its water plan by Wednesday, April 10.
The Michigan Department of Health and Human Services (MDHHS) said it needs more information to make sure McLaren Flint is taking the necessary steps to ensure the public's safety and health.
The health department has reviewed records of Legionnaires’ disease patients with inpatient exposure histories at the hospital over the past 16 months.
From its reviews, the health department said it found anomalies in the performance of secondary treatment systems in the hospital and identified issues with monitoring procedures.
The hospital has been requested to provide data showing its water management effectiveness. It includes water quality and bacteriological testing, as well as documents of implementing the hospital's water management plan.
McLaren was part of a Legionnaires' outbreak four years ago.
President and CEO Chad Grant wrote a seven page letter to the state.
Grant said from its own external review and clinical data, it did not support the state's findings.
The president and CEO said the anomalies found by the health department were instances of normal and expected variability in water quality.
Grant wrote the hospital has invested close to $2 million in its water management program to reduce the risk of legionella at the hospital over the course of four years.