A 13-year-old boy died and at least six other children were rushed to hospital unconscious after a carbon monoxide leak at a hotel pool.
Five people are in stable condition and one has been released, the hospital said.
Two others treated for carbon monoxide-related exposure included a Niles police officer and Berrien County deputy.
Six other patients - including the child who died - were taken to nearby Lakeland Hospital, spokeswoman Megan Yore said.
13-year-old Brian Watts was unresponsive and was pronounced dead on arrival at the emergency room.
The children range in age from about 10 to 14, officials said.
Niles Fire Department Mechanical Inspector Capt. Don Wise says a pool heater had improper ventilation.
A carbon monoxide leak is believed to have killed one person at the Quality Inn & Suites in Niles, Michigan, on Saturday. She had just been with the other children in the pool area and went into the room, where she became unresponsive.
Staff called 911, according to ABC News, and opened the doors to the pool area.
"I saw that EMS, you know, working on people just outside of the pool. and I saw one young lady just lying flat on her back motionless, foam coming out of her mouth", Nalian said.
The hotel has been shut down until repairs are made.
Carbon monoxide levels in the building were later found to be 16 times above the safe limit. The U.S. Occupational Safety and Health Administration prohibits workers from being exposed to more than 50 parts averaged over an 8-hour period.
The hotel has been closed Saturday as officials try to find the source of the leak.
It is unclear if there was a carbon monoxide detector in the pool area.