Thousands of students in New Jersey were unable to attend school Monday after a cybersecurity incident caused technical difficulties across the Freehold Township School District, administrators said.

Superintendent of Schools Neal Dickstein sent an email to families late Sunday night announcing that classes were canceled for the entire district, which includes an early childhood learning center, five elementary schools and two middle schools. Dickstein cited “technical issues related to a cybersecurity incident” and said the district “retained outside IT expert consultants who are working around the clock to assess, contain, remediate, and fully restore operations.”