At least 19 cadets at a military-style youth academy in the Washington, D.C., area were sent to area hospitals Sunday after reporting symptoms of an unknown illness, prompting a mass casualty response, officials said.

Emergency crews responded to the Capital Guardian Youth Challenge Academy in Laurel, Maryland, after cadets began experiencing symptoms following lunch, the DC National Guard said, according to FOX 5 DC.

The academy, which is operated by the DC National Guard, is a military-style life intervention program for at-risk teens, according to the institution.

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One mother told FOX 5 that blood tests at a hospital showed her son had elevated carbon monoxide levels. He reportedly developed delayed symptoms hours after other cadets were taken for treatment, including dizziness, headaches and nausea.

The mother added that the youth academy decided to temporarily close following the incident.

However, Anne Arundel County Fire Department officials said they conducted a carbon monoxide investigation and did not detect elevated levels of the gas, according to the local station.

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Officials have not confirmed the cause of the illness but said it could be related to food.

DC National Guard officials said the health and safety of cadets and staff remain their highest priority and that they are working with emergency medical personnel and public health authorities as the investigation continues, according to FOX 5.

Officials added that while 19 cadets were sent to area hospitals, one adult was evaluated at the scene and declined further medical treatment.

Fox News Digital reached out to D.C. National Guard for more information.