Baltimore County Public Schools systems and devices were struck in a ransomware attack late Tuesday, leading virtual classes to be canceled Wednesday.

The Teachers Association of Baltimore County is warning teachers to leave their computers off and not turn them on or check email until they receive word from the school system.

"We don't know at this point of a timeline but we are listening to our experts to guide us in the proper manner," Corns said.

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Police Chief Melissa Hyatt said police are in the "preliminary steps" of an investigation but declined to give any details.

County officials said there is no reason to believe the county's own systems were affected. However, officials said their network and devices will be inspected and security will be enhanced out of an abundance of caution.

In neighboring Baltimore City, school system officials said students without a device issued by the city school system would be granted an excused absence.

"Students participating in virtual learning should only use City Schools-issued laptops or devices," officials said in a note to families. "Do not use devices issued by Baltimore County schools or your personal laptop or computer.

Last year, the city government was crippled for months by a ransomware attack. Read more at WBAL