A botulism outbreak in Bristol Bay communities is being monitored by state and local health officials, according to the state Department of Epidemiology, which said Wednesday that more than 25 people have so far been linked to a batch of contaminated seal oil produced in the village of Twin Hills.

Alaska Dispatch News reports that several people have been hospitalized, some are being monitored and health officials are still trying to contact others.

The first botulism cases were reported Friday after two people were flown from the village of Quinhagak to Bethel for care. The two were later taken by medevac to Anchorage and remained on respiratory support Wednesday, reportedly unable to breathe on their own, according to a state official monitoring the outbreak.

Three others from Quinhagak were treated for symptoms of botulism, and others in Twin Hills and Dillingham have reported symptoms or are being monitored. One child has also shown symptoms of the disease, which can be fatal, according to Dr. Michael Cooper, the infectious disease program manager at the Department of Epidemiology.

“This is a very concerning outbreak,” said Cooper. “This is one of the largest clusters of botulism we’ve ever seen.”

An investigation linked the illnesses to a batch of seal oil produced in Twin Hills, and Cooper said testing conducted at a state lab revealed the oil was particularly toxic.

“When it was tested, it came back at the highest level the lab instrument can measure for botulinum toxin,” he said Wednesday.

The testing was completed Tuesday, and Wednesday morning, the state dispatched a second public health nurse from Anchorage to continue the investigation out of Dillingham.

“In an odd twist to this case, after we showed preliminary test results to the family who produced the oil, they sort of refused to stop eating or serving it,” said Cooper.